Sekai is in the same class as Makoto Ito and her best friend, Setsuna Kiyora. When first starting high school, she fell in love with Makoto who would later be assigned the seat next to her in class. Sekai is cheerful girl who cares deeply for her friends. She sets aside her own feelings to help Makoto gain the confidence to start dating Kotonoha because she wanted him to be happy, but quickly realizes that she is unable to accept that Kotonoha is the girl Makoto should be with.
Sekai also has a red cellphone in which she has a picture of Makoto set as her wallpaper, believing the rumour that if no one sees it, he will fall in love with her. When troubled, Sekai will usually turn to Setsuna for advice.
The Visual NovelEdit
In the game, Sekai, despite her crush on Makoto, decides to play the role of matchmaker for Makoto and Kotonoha.
Depending on the player's choices throughout the game, Makoto may start an affair with Sekai.
The ending also depends on the player's actions; Sekai can either end up together with Makoto or end her life. In rare cases, she's left alone and alive.
Sekai's role is largely the same, however, the series focuses more on Makoto's affair with Sekai, and the other girls in the series.
Sekai's role is largely reduced, due to have gotten sick with the mumps. She is mostly unseen except for at the beginning of the game, when she asks Setsuna to take her place at work, and a few other scenes.
The classic "Love Triangle" between Makoto, Kotonoha, and herself doesn't exist, because the story is set in a different universe.
But later in the story, Sekai and Makoto can become lovers.
- Sekai has fewer good endings in the game than Kotonoha.
- In the anime, Kotonoha says that Sekai was lying about her pregnancy due to her seeing nothing in Sekai's corpse. She could be wrong because a fetus would not have had enough time to develop long enough to be seen until weeks after being conceived.
- Sekai used to heavily believe in the phone wallpaper rumour even though she saw Makoto's wallpaper and Setsuna seeing Sekai's meaning that none of them would find happiness together (or so the rumour says).