Pet Mimamori Camera ni Ane to Otouto no Sex ga Utsutteta.

Rina has grown deeply attached to a stray cat recently brought home by her older sister, Mina, and her younger brother, Masao. Wanting to keep a watchful eye on the beloved pet while she is away from the house, Rina secretly installs a monitoring camera without telling any of her family members. The device runs quietly in the background, capturing everything that happens in the room throughout the day. Eager to check on the cat after her classes end, Rina remotely accesses the camera’s archived footage from the previous day. She reviews the recordings spanning the hours between the end of her regular school day and her arrival at cram school, expecting nothing more than ordinary scenes of her pet resting or playing around the house. However, the video reveals far more than she ever anticipated. Alongside footage of the cat, the hidden camera has inadvertently recorded an intimate and shocking secret: her older sister and younger brother engaging in sexual intercourse. What began as a simple way to monitor a rescued pet has now exposed a deeply hidden family scandal, leaving Rina stunned by the forbidden reality unfolding within her own home.