Aino Seiji is your typical high school student when he meets Guri, a shinigami! No, a pervert--no! An angel?! Guri introduces him to the Kiss Note and explains that if he doesn't kiss someone within 24 hours, she will die.
Guri finally meets Seiji's younger sister, Akua and is surprised by her rather cold attitude towards her big brother. The cupid decides to learn more about what changed this once loving sister, and Yuzu is right there to help.
Yuzu will go to great lengths for her beloved older sister, Akane, even skipping her own lessons to watch over her. Despite harsh words from Akane, Yuzu refuses to relinquish her forbidden love even for someone like Seiji.
In a desperate struggle to find Seiji, Akane and Yuzu seem oddly worried when Guri tells them that he is off with Shikimi searching for her crush. The concern seems warranted when Seiji finds himself in the midst of a torture session with Shikimi!
Seiji, Guri, Akane and Yuzu have invited Akua to go with them to the beach. Akane tries to get Akua to go swimming with her in attempt to get closer to Seiji's little sister, but Akua gives her the cold shoulder.
After an argument with Seiji, Guri goes wandering the city on her own. During a stop at the bookstore, a handsome stranger stops to talk to her. When the unknown young man invites Guri out on a date she can't bring herself to refuse.
Yuzu and Guri are off to save Akane! Several obstacles are placed in their path but the girls overcome them with ease, only to find that Akane is not herself. A happy reunion quickly turns to shock as Akane turns her blade on her sister.
It's time for the school cultural festival! Excitement is in the air as life seems to be back to normal for Seiji, Akane, and the rest, but all is not what it seems. Shikimi suddenly has transferred into Seiji's class and it now has Akane on edge.
As his family takes off for a few days, Seiji finds himself home alone. Except for Guri, of course. But the peace of the moment is short-lived when Akane shows up saying she's there to spend the night and to claim the kiss that Seiji had promised her!