Souta Takarada, who lives a closed life, is raised by Heine-san, a household servant. Heine-san has great style and is beautiful, but she is a bit dangerous, so Souta is always nervous. And Heine-san is really nice, and she always compliments me no matter what I do, so Souta's heart is always pounding. A mysterious life with an overprotective(?) older sister!