Shadows of Summer

Izumi's father invites him to spend the summer at his house by the sea, and Izumi only agrees because he can bring his girlfriend Sophia along so he won't be stuck alone with the old man. That plan backfires quietly: while Izumi relaxes and treats the trip as a carefree vacation, Sophia and his father start drifting into something that has nothing to do with being family.

The setup is simple and doesn't pretend otherwise. Izumi is the one enjoying his summer, oblivious, while the real story happens behind his back between Sophia and Kuroda, with the distance between them shrinking chapter by chapter.

You move through the story as Izumi, clicking through dialogue and scenes organized by chapter, watching a situation unfold that the protagonist himself can't see. The game keeps adding chapters and animated scenes as it goes, but the core is still just watching the slow unraveling from the wrong side of it.