Her younger sister turned into a gyaru and started coming on to me? (Yes, there’s some comeuppance too.)

After being betrayed and dumped by his girlfriend, the protagonist falls into despair. Just when he’s at his lowest, her younger sister suddenly shows up in front of him. For some reason, the once quiet and modest girl has transformed into a flashy gyaru overnight.

“Hey, Onii-san, w-wanna play some games with me?”

“That must’ve been really tough for you…”

Despite her dramatic change in appearance, her gentle and caring nature hasn’t changed. As she stays by his side, wholeheartedly supporting him, her warmth begins to heal his heart. Little by little, he finds comfort in her presence, and before he knows it, he starts to fall for her.

Meanwhile, the ex-girlfriend who betrayed him, along with the guy she cheated with, begins to spiral downward into ruin.