Open Sesame (Mutou, Hiromu)

On a rainy night, Takuma picked up a young boy who was soaking wet, thinking that he was a girl. But as it turned out, Ruka was a boy who ran away from home, and he decided to stay at Takuma’s apartment. The next day, Takuma takes Ruka to the kindergarten where he works and makes Ruka work there…?! And what’s the real identity of this mysterious boy?