Living in a vast home as a regular high schooler, Shungo's world is turned upside down when his sister Ryoko urges him to take in two siblings, Mayu and Mikihiro Tsukimura. Mayu's ongoing issue with androphobia prompts Ryoko to seek Shungo's aid in helping her conquer this fear. The solution? For Mayu to share Shungo's room, bed, and bathe with him. Adding to the chaos, the student-council chair Reika Hojo becomes their unexpected maid.