Mitsuki Igarashi moves to Tokyo to attend school and comes to live with her aunt's family. The household consists of her aunt and her cousin, Misuzu Kawanami. Mitsuki had only met Misuzu a couple of times as a child, and they hadn't seen each other in over ten years. Reunited after so long, Mitsuki is struck by how much Misuzu has matured into a beautiful woman. As Misuzu's gaze lingers on her, Mitsuki begins to grow self-aware, her emotions quietly stirred. Gradually, their relationship deepens.