Rui Tachibana (橘 瑠衣 Tachibana Rui) 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 a widower named Akihito Fujii, Rui becomes Natsuo Fujii's step-sister.
Rui is a slim girl with short blue hair (that temporarily grew her hair to shoulder length later in the series before cutting it back to its original length), bright magenta eyes and she generally has a blank expression on her face, accompanied by an equally monotone voice. These combined character traits has made her hard to read, leading to misunderstandings of her being anti-social. Over time, her face becomes more expressive, much to her chagrin since she gets teased for it.
In most of the manga, she is often seen wearing her uniform, which consists of the standard white collar shirt, sweater vest and a plaid skirt. After graduating from high school, she is often seen in casual clothing when not wearing a chef’s uniform for work.
At first glance, Rui is an aloof and blunt girl who is hard to read emotionally. Her standoffish personality has made it difficult for her to socialize. As her first meeting at a mixer, she didn't do much to interact with the others.
Once someone passes through her cold demeanor, Rui is actually a very kind and loving girl throughout the series. In spite of this, it can be hard for her to express her feelings towards someone she genuinely likes. She is very supportive of people she cares about, in spite of their flaws and even if their desires conflict with her own.
Rui has a tendency to pout when things don't go her way, though Natsuo finds this feature of hers adorable. Rui is also surprisingly easy to embarrass in spite of her stoic personality. When Natsuo lists all of her behaviors he finds cute, especially to other people in front of her, she becomes overwhelmingly flustered.
Rui is the younger of two daughters of Tsukiko Tachibana and her ex-husband, whom she divorced after he admitted to infidelity. Rui grew up having to deal with her mother's constant disparaging talk about her father, which upsets her greatly. This changes for the best once Tsukiko meets Akihito Fujii.
Rui felt like she grew up in the shadow of her sister, with Hina Tachibana seemingly appearing more attractive and outgoing. She also feels insecure about Hina's body developing faster than hers when they were relatively the same age. Nevertheless, she loves her sister dearly and is not afraid to be blunt with her. Both sisters are terrified of thunderstorms, but Rui is often comforted by Hina during those moments.
Rui goes to a high school on the other side of town, up until the events where she meets Natsuo Fujii.
At the start of the story, Rui was invited by her classmates to attend a mixer. This was her first encounter with Natsuo Fujii, who was also forced to go. Agreeing to the fact they were not used to this stuff, Rui and Natsuo skipped the mixer with her pretense of wanting him for something. The two strolled into the streets into her house which was empty at the time and then they headed straight to her room.
Without further ado, Rui asked Natsuo to have sex with her - not because she likes him or wants a boyfriend, but because she wants to experience it for herself and is tired of people speaking to her condescendingly about it. She also specifically chose Natsuo because he was obviously a virgin and didn't want someone experienced to take advantage of her or claim her virginity as a prize. Natsuo agreed to her reasoning, which led to their one-night stand.
After that night, both never met again, until they found out that their parents will be having a remarriage. This made them dumbfounded, Natsuo, in fact, was more confused since his crush (Hina Tachibana) and Rui (his first in bed) will becoming his step-siblings. As their visit to the Fujii resident was almost over, Rui acknowledged her mother remarriage and doesn't care because it's for the sake of her mother's happiness thus leaving Natsuo the decision on his own.
Rui with her sister and Ms. Tsukiko (Hina and Rui's mother) transferred into the second-hand house Akihito Fujii (Natsuo's father) bought by the next week while Natsuo and his father arrive with a transfer cargo later on. She eventually crosses path with awkward Natsuo, and agitated for his reaction. She asks him to pretend that it never happened in order to forget what was done, and left Natsuo on his own. A little later they assemble at the dining room after finishing their task of cleaning the house.
Rui's sister went out of the bathroom topless, only to get a sermon from their mother. Rui entered the bathroom next and as she went out of it, she saw Natsuo kneeling at the sofa; ready to steal a kiss from her sister but he aborted after seeing Rui.
Friendless transfer student
The next day, Rui transferred to the school Natsuo Fujii goes into at section 2-2. She was surrounded by her new classmates wanting to know her more but her bashfulness stopped her from communicating. Rui stared to Natsuo's curly hair and told him it's too messy. Rui was about to answer his question, however, Natsuo dragged her out of the classroom after bringing up about her mom.
As they arrived at the backside of the school building, Natsuo asked her of her sudden transfer. Rui then thought of their recent relationship could be boggling him and decided to tell her to ignore and not talk to her instead.
Natsuo persuaded her at lunch, but he got insecure instead of her eating alone. Rui told him about her past; her envy for her sister's energetic side and her friendly nature. She had also gone too far by copying Hina Tachibana's way of her speech though ended up as a silent type girl. She suddenly brought out again of his messy hair and offered to fix it for him. Then to his thought, he didn't exactly imagine Rui's such a thoughtful person from inside and out, just that her way of speech gives the others a different personality description.
Yet Natsuo couldn't stand it, to the reason he doesn't want her to be like that forever, and decided to help her out on her friendless struggle by doing some impromptu conversation where it leads astray. Their short comedy leads to the burst of laughter inside their room and the atmosphere Rui seems to be scared of disappeared; albeit she remains shy towards her classmates.
Hina the Mistress
Few days have passed after Rui's transfer, their family became used in living together and seems like problems might not come. Though, it was just the fabrication of false happiness as Rui knows about Hina Tachibana's (Rui's elder sister) affair to an adulterer.
One day, Natsuo Fujii left their family a message at his room; saying he'll be living at Fumiya Kurimoto's apartment for a while. This situation made their parents panicking into a point they thought Natsuo disagrees their remarriage. Yet it wasn't that at all as Rui sees her sister's worried expression and knowing her, she has something to speak for.
The next day, Rui searched for Natsuo even with the rainy condition and Natsuo saw her at the window of Fumiya's apartment. She asked him to allow her to stay for the night too but he rejected the thought. Without any doubt Rui left the apartment to search for an internet cafe to stay in however she was interrupted by Mrs. Kurimoto (Fumiya's mother) near the apartment entrance.
Without anything for him to say, Fumiya's mother welcomed Rui to their apartment. It caught him for her efforts to search him even with the bad weather, her sock and shoes were apparently wet due to his immaturity. Rui was also offered a hot bath by Mrs. Kurimoto and although very sudden, she wears a lovely pajama for staying in.
Fumiya arrived at their apartment only to be surprised for seeing a girl in his room. Suddenly his sister arrived as well and was surprised for it. After several minutes of chatter, Natsuo and Rui summarized the true situation, all the things Natsuo knows and the latter about Hina's affair to a married man. Unknown to what they must do to determine Hina's lover, Fumiya decided to make a master plan and together they created a descriptive and arranged blueprint to catch the adulterer.
When Natsuo and Rui returned to their home the next night, their parents sat inside the living room gazing at their divorce papers. It surprised them because the room was dark enough to tell that no one was there. Their parents thought it was their decision that brought this upon them, although their kids disagreed to it. Natsuo was slapped by his father for not bringing up his problems to him. His father would rather want him to share his thoughts because they are family, but for how things are made it impossible to share the thought. The little commotion was interrupted as Hina came down her room, tears filled her eyes, and meant to say her apology to Natsuo.
Their plan commenced the next day later in the afternoon. Both of her and Natsuo stalked Hina on her way to a busy street and into a stand-up bar, thinking her lover would appear but instead, they waited for hours as she drank her problems away. The next day, they followed her once again as she made her way in a hurry, and then only to be dismayed seeing her enjoying the chatter after her performance on a play. Their next attempt was also a disaster when they assumed that Hina will be meeting him this time; although it was a girlfriend. Lastly was the Plan "P" or likely Plan Phone. Rui snatched her sister's phone while she was taking a bath. Hina's phone suddenly rang and a name Shū Hagiwara prompted on the screen. Rui tried to mimic her sister's voice, yet her bashfulness controlled her over that made her hang up the call.
All their efforts were worthless, their plan to foil Hina's lover was rubbish, and the two reported to "Captain" Fumiya at L'amant. Yet as creepy as their plan was, the timing for them to see Hina and Shu came; at the same restaurant where they are. Without any doubt, Natsuo urged them to break up. Tension rose to both camps, L'amant's atmosphere somehow was filled with negativity until the owner to intervene; asking them all to head into the restaurant's far side.
The four sat together with Hina beside Shu while Rui was parallel to Natsuo. The owner prepared L'amant's special, a Neapolitan spaghetti, for all of them while telling Natsuo "The best way to converse is a stomach filled with food". Shu started the conversation by asking Natsuo if he'd be happy if his divorcement will be a success. Adding his love for Hina is serious and not just for pleasure. Natsuo's immaturity and indecisiveness hit him, having him hear it with his own ears struck him more for something he can't really avoid. Yet as Shu reassures his divorce will be almost complete, Rui had heard enough as she threw a glass of water into his face and ran out of L'amant. Rather than getting shocked, Natsuo followed Rui outside.
Rui ran as fast as she could. Natsuo followed her and called her out to stop. She stopped and felt mad about what she heard from his tongue, adding she'd gladly done it if Natsuo really can't have the courage to do it. Then she faced Natsuo with her eyes filled with tears as it ended with him embracing her, letting her burst her emotion til it subsides.
The next day, Rui went to the bathroom to wash her face, but instead, she saw Natsuo surprised at her messy hair just like him. She also asked him if her eyes' condition and gave him the thanks for comforting her. Both went off to the living room after that and they saw the calendar drew with a large flower with its stigma encircling the 12th of May; Mothers' Day. But due for running into many places stalking their sister, they never planned any present to give.
Later on, Rui was asked by Hina if she'll be accompanying her for buying a present, instead, she rejected. The same answer was given by Natsuo to Hina as he heads out to visit his mother's tomb. The sisters were given a bit of info to his activities and they both decided to head out and buy gifts together. Natsuo arrived late into the cemetery with a bucket and a dipper, Rui and Hina appeared behind him with presents to offer for his mother. Hina also announced her relationship with Shu as void for the time, all thanks to them both.
- The name Rui means "lapis lazuli" (瑠) (ru) and "clothing, garment" (衣) (i).
- It can also mean "tears".
- Rui's surname Tachibana means "orange, tangerine" (橘).