St Marris Academy is a facility training youma-hunters. Within their ranks are 3 elite students, Hikaru, Seira, and Yuki. A fierce battle unfolds when the youma Balmus invades the campus. However, the three are defeated when they are attacked by Kotone, a teacher at the Academy subjugated by the youma.
The Aoi siblings, Aki and Sora, are as close as a brother and sister can be. But as Sora enters high school, he realizes that his feelings for his older sister go beyond simple family ties. Oblivious to her sibling's affair, Sora's twin sister Nami attempts to get her best friend to go out with him. And unbeknownst to either of them, Nami harbors a deep and jealous lust of her own. Aki-Sora is a love story, for sure, but whose love will be returned? Whose love goes unrequited? Can the bond between brother and sister be strengthened by romance, or will Aki's and Sora's affection drive them apart?
Makoto, Sekai, Kotonoha, and many other classmates all go to a hot springs hotel to relax, where they discuss what their plans are for the upcoming Valentine's Day. When the day actually comes, half a dozen girls fight over who gets to give chocolate to Makoto.
