You play yourself, dropped into the world of Chainsaw Man — except somewhere along the way, Sans, from the video game Undertale, ended up bound to you. Not possessing you outright, not replacing you — he's a separate presence sharing your existence, carrying his own strength, his own voice, and his own lazy, deceptively dangerous nature. Most of the time, you're fully yourself, in full control. But sometimes, without warning, he takes over — speaking, acting, and fighting as himself, with you either watching helplessly from somewhere inside, or slipping back in only once it's already happened.