FSDSS-519 Bitterly watching his lover being fucked by the manager

The main character starts dating Kaname, a very popular girl with big breasts at the family restaurant where he works part-time. However, the manager, who was jealous of her, forced her to have sex with him. At first she didn't like it, but gradually she was seduced by the manager's big cock and rough attitude. Finally, our good man discovers how the manager is ravaging his girlfriend. Such is the boy's fate.