Blind Love

Shou, the son of a gang member, became the right hand man of Taiki, the gang leader's son. On the way back from his high school entrance celebration, Shou runs into his long-time crush, Kunie, Taiki's cousin. Shou goes to Kunie's home on his request, but once there, Kunie asks him to become his. Shou refuses because of his allegiance to Taiki, but Kunie drugs Shou's drink and takes advantage of him!
(Source: MU)