Sei ni Kyoumi ga Detekita Otouto ni Jikan Teishi Appli wo Ataete Mita

An older sister notices that her younger brother has recently become curious about sex. Deciding to have some fun with him, she gives him a fake time-stop app on his phone and pretends that it actually works. When the brother activates the app, believing he has frozen time, his sister plays along by staying perfectly still, allowing him to explore his newfound interest without resistance. However, as the brother becomes bolder in his actions, the sister finds herself caught in her own game, leading to a series of increasingly intimate and awkward situations between the two siblings. The line between joke and reality blurs as both discover unexpected feelings, turning a simple prank into a complicated and risqué encounter that neither of them anticipated.