Shounen Tsubaki

Tsubaki was adopted as a young child and has never left his foster home since. On the surface, he is treated well by his foster family, yet his foster father only uses him for sex and his foster mother ignores him. His only contact with the outside world is the kind teacher next door, Koga-san, who gave him his name, and Koga-san's younger brother, Hayato, who has slept with Tsubaki since the first time they met. Between the two, who will save Tsubaki from his cage? Who does Tsubaki want to save him?