Mary and Masaki are step relatives. Mary is beautiful, close in age, and overflowing with motherliness, so Masaki was desperately trying to suppress his sexual desires for her. However, the more he suppressed his lust, the more Masaki's mind and body deteriorated. Unable to endure it any longer, Masaki decided to leave home, but just then, they ended up going on a hot spring trip together as a family of three. He thought this would allow him to finally sever his feelings for Mary…
