"Eh...? Y-You're kidding..? You mean we're going to be separated, Onii-chan? I'm too scared to even leave my room without you..." My little sister Mei loves staying at home. It sounds nice, but to put it bluntly, she's just a shut-in. Though there was a reason for it, Mei now rejects even our parents and refuses to see anyone but me. She's completely dependent on me. It's about time she moved on from me... the truth is, I... want to be free from Mei. But she has no such intention, and my parents are apparently desperate not to lose me as her caretaker. Then one day, I came across a story: "A former plain girl became a black gyaru under her boyfriend's influence and reinvented herself." "I see, that method could work...!" I couldn't sit still any longer and burst out of my room. My destination, of course, was Mei's room.