Minori Koganuma is a supporting character of the Outbreak Company series. She is another one of the ambassadors from Japan, assigned to serve as both a bodyguard and an advisor for Shinichi. She's generally the realist to Shinichi's idealist, and a fujoshi. She is normally easygoing. She has a younger b/f who loves her large chest and will protect them the tendency to use her gun to calm an argument. She has the tendency to snark when Shinichi is staring at her breasts. She doesn't seem so at first. But we see she is obsessed with BL, yet is still a competent member of the JSDF. She also does not tolerate perverts and lechers as seen when she ruthlessly beats up the JSDF men who are peeping on her and the other girls at the beach.

Petralka Anne Erdant III is one of main characters of the Outbreak Company series. She is the current queen of Eldant. She is a bit hot-tempered and easy to annoy but cares for her kingdom. She hates being called a "Young Girl", and even punched Shin'ichi for calling her one at their first meeting. Petralka is insecure about her chest has shown jealously of other girls that have larger cup sizes. She is one of the first in the Holy Empire of Erdant to master the Japanese language. From the start Petralka has shown an interest in Otaku Culture, but didn't have a full understanding of it. As a result, she would visit Shinichi to read manga together. When Myucel started learning Japanese and kanji, Petralka began to learning it herself. Not wanting to be outdone by a nonhuman and someone of a lower class. She learned the language fairly quickly, and is capable of having conversations in Japanese without the magic ring. She is shown to be jealous alot. Petralka usually demands attention from Shinichi, and only him. She tends to give Shinichi a leery look whenever he fawns over girls who are obviously much more well-endowed than she is. In episode 6, one of her first comments upon suggesting that Shinichi gets a new maid to help Myucel if she teaches at school is to sarcastically ask if he wants "another large-breasted maid". Whenever Shinichi makes any sort of request from her, her first reaction is to assume he has sexual motives for doing so, such as favoring Myucel to impregnate her, or wanting to save Elbia to have a big-breasted animal girl as a mistress. The twist, however, is that she only looks like a child and is really a teenager. Because of the circumstances of her coronation as Empress, Petralka is determined to prove that she's a wise, just and competent ruler. Unfortunately, this makes her desperate to save face when undermined, and she typically takes it hard if criticized.

Myucel Foaran is one of main characters of the Outbreak Company series. She is a half-elf who is Shin'ichi's maid in the Holy Eldant Empire. Having no discrimination at her origins, Shin'ichi quickly befriends Myucel and starts teaching her the Japanese language. In response to his kindness, Myucel eventually falls in love with him and becomes his most trusted supporter. Myucel is a powerful mage who was trained in the Eldant military. Since she is a half-elf, she is disdained by both elves and humans. For that reason, Myucel often hides her elf ears. However, she started showing them whilst in the mansion when Shinichi, found out about her heritage and praised Myucel for it instead of ridiculing her. Myucel often thinks of herself as a lowly servant. Often talking down about her self. However Shinichi did not see Myucel for her class and often treated her as an equal. She takes a knife for Petralka, and miraculously survives. When Shinichi first spots her elf ears, he's taken aback by it. She immediately apologizes, thinking he'd be upset by it, as half-breeds like her are looked down upon. But he instead finds them quite attractive. She has undying loyalty towards Shinichi. It gets to the point, if she cannot save him, she is willing to die with him.

Kengo Tanabe is an antagonist in Chapter 156 from Domestic na Kanojo. Initially coming off as a charming man, Kengo is actuality an abusive individual when it comes to relationships. He briefly dates Hina Tachibana, but after being rejected, Kengo began stalking her. After further intervention which led to him getting fired, Kengo went to stab Hina, but ended up stabbing Natsuo Fujii instead, which led to his imprisonment. In Chapter 266, he secretly hired the journalist, Takeru Okunugi, in an attempt to expose the picture of an affair between Hina and Natsuo to the public since Natsuo's fame rose. But his plan was ultimately foiled by Hina with the help of Reiji Kiriya, Kengo claims the truth will come out and will scream her indecency from the rooftops when he plans to leave a jail. Only being coldly look down by Hina, she leaves him behind after defiantly tell him: "Go ahead". Enraging by this response, Kengo yells at her before being tasered and dragged back to his cell by the prison guard. He is never seen or heard for a while, but it is implied that he has served a life in prison due to his repeated denial over crimes at trial, thus bringing his threat to an end once and for all.

Kazuyuki Kine is one of Natsuo’s friends, often called "Kazu" by his peers. Like Yūya, he has a flashy and carefree personality, fitting the stereotype of a "playboy."

Yuuya Masaoka is a friend of Natsuo, often referred to by his nickname "Yūya." He has a flashy, playboy-like personality, and although he has a girlfriend, he is notorious for his bad habits with women and love for group dates. Despite his appearance, he attends a prep school. It is revealed that he once had a physical relationship with Momo.

Akihito Fujii is the father of Natsuo Fujii who began to date Tsukiko Tachibana after Jun Fujii (Akihito's wife) died and he becomes the stepfather of Hina Tachibana and Rui Tachibana after remarrying Tsukiko. Outlandish behaviors, such as remarrying or moving out without consultation, are often observed. Even now, after the death of his ex-wife, Jun, he always visits her grave on the anniversary of her death.

Shū Hagiwara is a teacher and the ex-boyfriend of Hina Tachibana due to fact that Shū is married, therefore his relationship with Hina for the last two years is an illicit affair and he also seems to have a good friendship with Reiji Kiriya. Shū is a friendly and thoughtful person who has a playful side to him, owing to his puppets and ventriloquism skills. According to Reiji Kiriya, Shū was constantly sad and fatigued with having to deal with his wife. Because of his unhappy marriage, Shū was ready to take risks with his affair with Hina Tachibana. Unfortunately, he has been indecisive on ending the marriage for some time. When he noticed that Natsuo Fujii was in love with her as well, Shū was a bit vexed, but nonetheless let Hina choose between him or Natsuo.

Reiji Kiriya is a professional author and teacher who publishes under the pen name of Yōu Hasukawa. He teaches Modern Japanese at Natsuo Fujii's high school and the monitor of the Literature Club. Kiriya has a friendly relationship to Shū Hagiwara, leading him to know Hagiwara's situation with Hina Tachibana. Kiriya has a cool and laid-back demeanor who is considered an odd ball by other teachers, but his work as an educator is flawless. He is understanding of complicated relationships, and believes love can transcend age, gender, as well as social norms and status. Kiriya has a playful side to him as he is known to tease his students. As mellow as he may be, he's not above strong-arming Natsuo Fujii into joining the Literature Club, especially after noticing he borrowed a book without permission.

Masaki Kobayashi is the owner of L'Amant (French for 'The Lover') restaurant and a former Yakuza. He's an openly gay man and prefers to be addressed as Marie, although he is often addressed as The Master or Mari-san by others. is coworkers are Fumiya Kurimoto and Ayano. Kobayashi tends to aid Natsuo Fujii and others by providing advice and consultation. Kobayashi is a strong and athletic individual who keeps himself in shape with various exercises, including yoga. He is very high maintenance as he keeps his body hairless and well moisturized and he wears expensive cologne. Kobayashi is a bright, cheerful, and flamboyant person. He often speaks in an effeminate form of speech. Because of this, he can speak on the same level with the females of the series, and can even be quite snarky with them. Kobayashi insists that people call him Marie or Mari-san and he gets irked when people address him by his actual name. Kobayashi is an empathetic person, sensing when others are emotionally disturbed and offers whatever advice he can - though sometimes that can come with a consultation fee of having to buy a drink from him. Kobayashi is also flirtatious, often teasing Natsuo Fujii and asking any men he meets if they're single. Kobayashi used to, and occasionally continues to put on a masculine, gangster persona in order to better blend in during his Yakuza days (sometimes he still does, until someone knows his real personality). However since coming out he has become happier and more true to himself. In spite of not allowing violence to occur in his restaurant, he is not above using a customer's romantic quarrel for his own - and other customer's - entertainment.

Fumiya Kurimoto is Natsuo Fujii's best friend and confidant. He is a waiter at L'Amant along with Masaki Kobayashi and Ayano. Kurimoto lives in an apartment with his mother and younger sister. Before high school, he used to attend the same class as Natsuo and lived in the same apartment building. He is currently attending Tokyo University with aspirations of becoming a lawyer. Kurimoto cares for Natsuo Fujii and he has his best interests at heart. Kurimoto will always help him out whenever he can, whether its to listen to his problems and offer solutions, or let him stay over in his room if he's having problems at home. Despite that, Kurimoto is envious of his encounters with women, and he will express his disdain verbally or by putting Natsuo in a wrestling hold. Although Kurimoto is older and in college, he longs to have romantic experiences with women and he is especially attracted to older women.

Natsuo Fujii is the main male protagonist of Domestic na Kanojo. He is introduced as a second-year high school student who loves writing novels, so he frequently heads to the rooftop during his lunch breaks to develop his passion for writing. It is there that he meets the beautiful new English teacher, Hina Tachibana, who not only becomes a source of inspiration, but his first crush and later his wife. In response to Hina's continuous reminders of his youth, and the belief that his love for her would remain unreciprocated, he decides to accept the proposal of Rui Tachibana, a cute but odd girl he meets at a mixer settled at karaoke by his friends. Both end up having their first sexual experience together, after which she tells him to forget about it and expect to never meet again. Just days later, his widower dad tells him that he is getting married again. That same afternoon, they are paid a visit by Tsukiko Tachibana (Natsuo's stepmother-to-be) and her two daughters who, to his absolute shock, turns out to be his teacher Hina and her sister Rui. Upon graduating from high school, Natsuo takes a placement test and succeeds in becoming a student at Meiji University. It is there that members from the drama club Forester took notice to his abilities and invite him to become a script writer for their plays.

Miyabi Serizawa is a college student and actress attending Meiji University, a prominent member of the college drama club Forester who has been the lead actress in many of its productions and the childhood friend of Yuka Kusanagi. Miyabi is generally a confident, if not prideful person with a passion for theatre. Her love of acting is so strong, she will refuse to partake in any performances if she feels like the people responsible for developing her role lacks the same drive she has. Miyabi can be confrontational about her roles on what kind of lines she has and how to deliver them. This has led to bad communication and discourse in her drama club in high school. In contrast, Miyabi is easily flustered when she herself experiences romantic and sexual feelings towards someone. In spite of her skillful acting, she is quite clueless on how to portray a seductive character, owing to her being a virgin and having no romantic experience whatsoever. This disturbs her greatly as she goes to extreme lengths to get in touch with her sexuality, including making a friendship with a promiscuous student that actually dislikes her behind her back. She has a rather pure perspective of love and romance, and sees anything outside the norm like multiple partners or step-sibling relations to be immoral and indecent. That perspective, however, appears to be questionable as she tries to make a move on Natsuo Fujii while knowing that he is currently in a relationship.

Hibiki Mikimoto is the step-daughter of Jou Mikimoto from his second marriage. After Jou remarried, Hibiki became his step-daughter. She attends a junior high and high school for young girls and is characterized by her baby face and short stature. She was affectionately called "Bikki" by Natsuo, a name she did not like. Contrary to her appearance, Hibiki has a mature personality. Her biological father separated from her biological mother due to a relationship with a hostess. During her first appearence, she accidentally met Natsuo, who had been separated from Rui, and used Natsuo to give her a ride on his shoulder to search for her stepfather and her mother. Later, she reappeared as Jou's step-daughter when Rui began working at his restaurant, and since then, she has been friendly with both Natsuo and Rui.

Haruka Fujii Tachibana is the daughter of Natsuo Fujii and Rui Tachibana who was born in 2016, early in the season of Autumn. After the three year time skip Rui gives Haruka the conjoined necklaces that Natsuo bought for himself and Rui as a sign of their love. Haruka is shown as a happy and cheerful girl.

Tsukiko Fujii, née Tsukiko Tachibana is the mother of Hina Tachibana and Rui Tachibana who began to date Akihito Fujii after Jou Mikimoto (Tsukiko's ex-husband) left her for another woman and Tsukiko becomes the stepmother of Natsuo Fujii after she got married to Akihito. Tsukiko is a kind and warm woman who is pleasant to be around that she tends to think of others before herself and almost divorces Akihito Fujii because she thought their marriage put a strain on their children (it was mutual decision between them both). She is very loving towards her children, as well as her step-son, Natsuo, in spite of not being his birth mother. Rui reveals that before meeting Akihito, Tsukiko had gone through a dark period in her life after her ex-husband's infidelity. By her own admission, she was incredibly bitter and hateful after the divorce, and felt like she could not trust men again. She has long spoken ill of her ex-husband to her daughters, which had a negative affect on Rui Tachibana. However, this changed upon meeting Akihito. After seeing his sincerity and hearing his genuine vow to support her, Tsukiko gradually overcame her depression and bitterness thanks to Akihito's sincerity and devotion, leading her to fall in love with him. Tsukiko has since been full of joy after meeting Akihito.

Yuri Umeda is a very attractive young woman who works hostess at an unknown club.Yuri Umeda or Juri (professional name), is a cabaret girl who helps Natsuo as the subject of his study material when he worked under Tougen Shigemitsu. A floor lady at the "Yoi no Chou" girl club. Her stage name is "Juri." She is originally from Akita Prefecture. Juri is Natsuo's first interview subject. She moved to Tokyo with dreams of becoming an actress but was unable to achieve her goals. She regretted ending her long-distance relationship with her high school boyfriend, Motoki Nakabayashi, who had always been kind to her. She broke up with him, choosing to escape from his kindness. After being persuaded by Natsuo, she returned to Akita to visit Motoki, only to find out that he had already passed away from leukemia. Although she couldn't reunite with Motoki, the experience gave her a chance to reflect on her past, and she decided to pursue her dream of becoming an actress once more. She is now a member of a theater troupe and continues to perform. Juri noticed the subtle tension between Natsuo and Rui just before they started dating. She gave Natsuo the advice, "Don’t let go of the hand of someone important to you."

Miu Ashihara was the former president of the Literature Club. Miu is portrayed as a shy and soft-spoken girl, with a sense of strictness when they are in the library. However, she also has an innocent vibe and can be awkward at times, especially when she’s around her adviser, Kiriya. Her bashfulness is more intense than Rui Tachibana's, and she often struggles to express herself comfortably in social situations. She has a crush on Kiriya but is very reserved in expressing her feelings. Despite her quiet nature, Miu is a dedicated and passionate reader.

Momo Kashiwabara is a supporting character. She is a member of the Literature Club and a friend of Rui Tachibana. Momo fits the 'Genki' female archetype in manga as she is constantly a energetic girl with a bubbly personality who is also incredibly eccentric and overly friendly to some people as shown when she gave Rui Tachibana a nickname and one of the dolls from her bag upon their first meeting. As noted by the girls in her class, Momo is also very flirtatious towards boys, flirtations that are rumored have evolved into relations on more than one occasion. She also exhibits a childish side, as shown by her nicknames like "Rui-Rui" and calling it "making love-love". As of Chapter 10, she has a massive crush on Natsuo Fujii, which has often gone to clinging to his arm and feeding him boxed lunches she made without his knowledge. However, beneath her flirtatious and bubbly nature lies deep vulnerability and a possible self-loathing. As revealed in Chapter 16, her parents have a very bad relationship and the are almost always working, which leaves Momo by herself for nearly whole days on end. As a result of this and her poor relationships with her peers, she once began self-harming. One of the reasons she loves Natsuo is due to the fact that despite knowing about her self-harming and her attitudes towards boys, he is still nice to her. It is shown that Momo is actually very smart despite her childish nature. In Chapter 20, Miu Ashihara notes that she knew Momo's name because she often sees her name in the top-ten school rankings. In Chapter 23, she mentions that she doesn't need to write notes in class. The reason her test scores drops on occasion are because she was in a relationship during that period. During the School Festival, she was able to see through Saki Kusumoto's lies where she deduces her relationship and grudge with Reiji Kiriya.

Rui Tachibana is one of the main female protagonists of Domestic na Kanojo. She is the younger sister of Hina Tachibana, but soon after Tsukiko Tachibana (Rui's divorced mother) marries Akihito Fujii (Natsuo's father), Rui becomes Natsuo Fujii's step-sister. At the beginning, Rui was aloof and emotionally reserved, often coming off as blunt and hard to read. Her cold demeanor and lone-wolf attitude made socializing difficult for her, and when she first appears at a mixer, she doesn’t make much effort to engage with others. Her early personality reflected her struggle to express emotions, and she often seemed indifferent to those around her. However, beneath this tough exterior, Rui is a deeply kind and caring person. Though it was hard for her to express her feelings at first, especially towards those she genuinely cared about, she proved to be extremely supportive, accepting others' flaws and desires, even if they conflicted with her own. She tends to bottle up her emotions, but as the story progresses, she learns to open up, and her warmth becomes more evident. Rui’s stoic and blunt personality hides a more playful side; she has a tendency to pout when things don’t go her way, a quirk that Natsuo finds endearing. Despite her usually composed demeanor, Rui is surprisingly easy to embarrass, especially when Natsuo teases her by listing all the things he finds cute about her in front of others. This causes her to become flustered and self-conscious. As the story progresses, Rui undergoes significant emotional growth. Her relationship with Natsuo helps her to become more emotionally expressive and socially open, which also leads her to embrace her own aspirations of becoming a chef. Rui’s character arc is marked by a gradual transformation from a distant, emotionally restrained girl to someone who is more in touch with her feelings, her desires, and her connections with others.