Kyousuke is the seventeen-year-old main character. He describes himself as average: he has average grades, lives in an average family (upper-middle class with a father, mother and sister), and has average physical features. Currently, he attends an average high school with Manami (later, Kuroneko as well); he begins the story as a first-year, but he becomes a second-year during the events of the novel. As far as future plans, he intends to attend the same local university as his childhood friend, Manami.
At the beginning of the series, Kyousuke and his younger sister, Kirino, have a distant relationship. Kyousuke says that they entered a “cold war” of sorts a few years ago, but the details of this cold war have yet to be revealed. After years of coldness between the two, things suddenly change when Kyousuke finds one of Kirino’s adult games and learns that she is an otaku. Through this, he tries to be a supportive older brother while realizing that he knows very little about his sister (for example, Kyousuke was oblivious to the fact that she was a model, a track star, and one of the top five students of the prefecture). Kyousuke feels somewhat belittled by Kirino’s accomplishments, but he learns to take pride in her.
After discovering Kirino’s secret hobbies, Kyousuke provides Kirino with “life counseling” at her request. During this “life counseling,” Kirino forces Kyousuke to play eroge. Kyousuke now considers himself to be a bit of an otaku and often refers to situations and people using otaku terms (e.g., flag events, tsundere, yandere). Trying to be a good brother, Kyousuke offers to accompany Kirino to her offline meet-up. This introduced him to Saori and Kuroneko; both of them have become his friends. Additionally, Kyousuke is friends with Manami, one of his childhood friends. Some of Kyousuke’s classmates assume that Kyousuke and Manami are going out, but Kyousuke denies this. When Akagi asked Kyousuke if he would be okay if someone started dating Manami, Kyousuke said that he would be uncomfortable with the situation.
Kyousuke is a good-hearted character and is extremely loyal to his friends and Kirino. He’s willing to take risks for them and help them at any cost. When Kuroneko started attending the same high school as Kyousuke, she was without any friends; however, Kyousuke joined the computer research club with her, despite being ignorant about anything concerning computers, in order for her to meet new friends. He has shown the same amount of concern for other friends as well as his sister on several occasions.
He and Kuroneko date for a while, but she ultimately breaks up with him. After witnessing his sadness firsthand, Kirino tries to get them back together, but Kyousuke decides not to when they approach Kuroneko and he learns Kirino wants to be the number one girl in his heart.
Later, his parents force him to move out after they express their discomfort in his relationship with his sister. Whilst he is living alone, Ruri, Ayase and Kirino argue over who should take care of him as he needs someone to cook him meals. Eventually everyone agrees that Ayase should be looking after him while he studies as she hates him the most. After the two months, he moves back home and his parents reveal that they knew about it all along and simply used Kirino as an excuse to get him motivated to work.
He eventually develops into a siscon and has impulses toward her, stating that he was beyond cure.
In the OVA’s for OreImo Season 2, he finally confesses to Kirino after turning all the other girls down, and Kirino returns his feelings. As the two plan to get married, they hit some situations where they might not be completely accepted by other people due to the immoral relationship between the two. In the end, they get married, but then go back to being siblings afterwords.