SONE-832 My Girlfriend's Big-Titted Little Sister Obviously Wants to Fuck Me, So She Deliberately Misses the Last Train and Stays Over at My Place Miyu Kohinata

The male protagonist's girlfriend has a busty younger sister who clearly has a crush on him. She deliberately misses the last train and comes to stay at his place overnight. With the girlfriend absent, the sister approaches the protagonist with various excuses, wearing revealing pajamas to deliberately seduce him. Alone in the same room, the atmosphere heats up with ambiguity, the sister boldly confesses her feelings, ultimately leading to a passionate night and the start of a taboo physical relationship.