That Summer, I NTR'd My Friend's Girlfriend

A visual novel set during the final weeks of summer vacation before the new college semester. The protagonist's roommate brings his girlfriend to stay at their shared apartment for 20 days before they move out together. As the three live in close quarters, the dynamics of the living arrangement begin to shift and evolve. The game is a mouse-driven relationship simulator where players gradually deepen their bond with the heroine through various interactions—minigames, gift-giving, and time spent together. As intimacy increases, new events and branching storylines unlock, culminating in fully animated adult scenes with multiple possible endings.