Ore no imouto ga konna ni kawaii wake ga nai

Kirino and Kyosuke head back to their hotel room to try and sort out their next move after agreeing that siblings cannot get married in real life. Kirino gets distracted with her newly bought eroge and finds that her feelings are too mixed to too concentrate on the game. Kyosuke then gives her a Christmas present which turns out to be the same ring she had asked him for the year previously, and ceremoniously puts it on her finger as a pseudo-engagement ring. Kirino reveals that she had planned on confessing to Kyosuke herself, but ran off earlier thinking that he was referring to his love for another girl. Having already given thought into their next move, Kirino shares this with Kyosuke. Sometime later, the siblings formally acknowledge their relationship to Saori and Ruri, the former of whom remains uncertain on her standpoint on the matter. After Kirino gets into her usual Meruru debate with Ruri, Kyosuke leaves to meet up with Kanako following her latest concert.

Kirino reminisces on her childhood, when she was very fond of Kyosuke and always looked up to him, until he stopped giving his all and adopted a more relaxed lifestyle. Blaming Manami for the sudden change in him, Kirino confronted her, asking her to give back the brother she loved so much, just to hear from her that the Kyosuke she envisioned never existed in the first place. To get back at Kyosuke, Kirino focused to improve herself and started avoiding him. Years later, she starts working as a model and befriends Ayase, but also develops her otaku hobbies, and becomes too ashamed to share them with anyone else. The issues she had with her secret were what somehow reapproached her with Kyosuke, who since then always stood by Kirino's side to support and protect her, even though she no longer sees him as the brother she once idolized.

Concerned by how seemingly close Kyosuke and Kirino have gotten, their parents arrange for Kyosuke to live on his own so he can focus on his exams. With Kyosuke needing to earn an A grade before he can move back, Kirino adds that if he does succeed, she'll do any one thing he asks. Later, Kanako decides to pay Kyosuke a visit in his new apartment, proving awkward when she finds an eroge Kirino lent him. She proves smart enough to guess that Kirino is his sister, but is still oblivious to her being an otaku. The next day, Ayase visits Kyosuke to deliver a housewarming present, shortly followed by Ruri, leading to an awkward and embarrassing confrontation. After Ayase takes her leave, Kyosuke and Ruri reconfirm their stance on their relationship, with Kyosuke stating he won't start dating until he settles things with Kirino.

After hearing no word from Ruri following their alleged break up, Kyosuke is shocked to learn from Sena that Ruri has transferred schools, later finding her house completely vacated. Troubled by this, Kyosuke comes to Kirino, who gives him his own life counselling and decides to help him search for her in a hot spring town. After they eventually manage to find her, Ruri points that Kirino hadn't truly accepted her dating Kyosuke, forcing her to confess her true feelings that she didn't want him to have a girlfriend, which was the reason she passed off Kouki as her boyfriend. Kirino states that despite this, she doesn't want to see her brother cry even more than that and wants to get the two back together to repay how much he has supported her over the past year.

With Kyosuke unable to give her a straight answer, Ruri asks that he give her his response after the party the next day. Speaking with both Kirino and Manami, they both tell him to think over this decision carefully. During the party, Kyosuke thinks back on the past year after he began his life counselling with Kirino, whilst also taking an opportunity to tease her. After the party, Kyosuke agrees to go out with Ruri, officially making them a couple. As Kyosuke becomes stressed over how to act like a proper boyfriend, he brings Kouki along with him to the Games Research club, where the other members claim that they always knew Kyosuke and Ruri liked each other, and are surprised to learn that they decided to go out just recently. After being given some time alone, Ruri admits she has also been stressing about how to act in front of Kyosuke and simply asks that they go on a date.

Kirino asks Kyosuke to pretend to be her boyfriend whilst they meet with a company director, Misaki Fujima. Misaki wants Kirino to work abroad as one of their exclusive models, forcing Kirino to have Kyosuke to act as her boyfriend as a reason not to leave. As such, they end up going on a 'date' together in order to keep up the act in case Misaki is spying on them, which proves more awkward when Manami sees them together. Whilst stopping at a place to eat, they encounter Kanako and her model acquaintance, Bridget Evans, and are forced to act in front of them too. Things become even more awkward when they encounter Ruri at the arcades. At the end of the day, Kirino becomes disappointed by Kyosuke's behaviour, saying she'll use a 'real boyfriend' next time. After Kyosuke clears things up with Ruri and hears her thoughts, he asks Kirino directly if she has a boyfriend, only to receive a cryptic response.

As Kyosuke, Kirino and Ruri decide to visit Saori's apartment as a surprise for her birthday, they finally see what she looks like without glasses. Four years ago, Saori was a weak bodied girl who was shy about showing her face to others. One evening, she was brought by her older sister, Kaori, to a special apartment where she indulges in otaku activites alongside her flatmates, Shinya Sanada and a budding manga artist named Kanata Yamanashi. Kanata took an instant liking towards Saori and soon taught her about the otaku lifestyle. However, the circle soon starts to dwindle after Kaori left to get married, leaving Saori alone once more. Feeling betrayed by Kaori, Saori became determined to start her own circle and help others like she helped her, receiving her trademark swirly glasses from Kanata to help her on her way. This would eventually lead to the start of her otaku life and her meeting with Kirino and Ruri.

As Kirino organisings thing with school and friends following her return from America. Kyosuke grows concerned that she might start ignoring him again due to the way he forced her to come back, as well as struggling to find the meaning behind the kiss Ruri gave him when he went to retrieve her. Later, Kirino once again calls upon Kyosuke for life consultation, having him take her to Akihabara to watch a trailer for the next Meruru season before engaging in a long-missed shopping expidition she spent the entire night planning. As thanks for his help, and to celebrate a year of life consultation, Kirino gives one of her eroge purchases to Kyosuke to play.