Shin Megami Tensei: Persona (1996)

In one of the school rooms, there's a poster of a woman stripper wearing a very revealing swimsuit and showing her stomach despite the game being rated K-A.

Near the end of the game, when the player is trying to find the real Mary soul in the underground Shrine Cave, she is actually undressed in a bubble showing her breasts which has somehow slipped in a game rated K-A.