A teenage shota who lives alone meets a girl named Misa Ayune. Large breasts, clear skin like porcelain, blue hair with pink streaks, and eyes often closed. But those eyes...they look like a galaxy. He sees them...and survives, which has her decide that as his "reward" she'll live with him as his sister! Going to school with him, cooking him meals, and eventually this relationship turns romantic...and yes, sexual too!