In the muted light of a shared room, Japanese siblings find themselves drawn to one another, their eyes lingering on the curves they've known all their lives. The brother, a tower of restraint, watches as his sister's breath hitches, her body betraying her as she catches him staring. He's rock hard under his loose pants, her eyes flicking down to the bulge before snapping back up, a flush creeping up her neck. She tentatively reaches out, tracing the hem of his shirt, and he sucks in a breath, his resistance crumbling.