Naoto finds himself living alongside his new stepmother and stepsister after his father's remarriage, yet he cannot ignore the growing emotional gap with Yui. Discovering a remarkable app on his phone, he decides to use it on her, resulting in an astonishing body possession that lets him see the world through her eyes. Returning to her room in confusion, he encounters her reflection in a full-length mirror, triggering an overwhelming surge of feelings that he finds impossible to resist.