Sena is Akagi Kouhei's little sister. While at first she pretends otherwise, Sena is a fujoshi, or "rotten woman" (a woman who loves yaoi). She often fantasizes about it; the idea of her brother and Kyousuke having a homosexual relationship is particularly pleasing to her. While she denies it, she is a brocon and has feelings for her brother. It is also shown that her brother cares deeply for her and, as Kyousuke says, is "a total siscon."

Sena is also part of the Computer Research Club, along with Kyousuke and Kuroneko. For a period of time, Sena quit the club, because the club was unwilling to create her video game for a contest. Kuroneko, her partner for this contest, was forced to work on it by herself; however, while Kuroneko is good at writing, she cannot program as well as Sena. The video game that Kuroneko had too many bugs to work. In the eleventh hour, Kuroneko was forced to ask Sena for help, who surprisingly agreed. Fittingly, Sena wants to become a computer programmer.

Finally ending Kuroneko's inability to make friends at high school, Sena becomes friends with her. The nature of their relationship is unknown, but Kyousuke is glad that Kuroneko finally was able to befriend someone.