Rui Hinamata lives a normal life as a high school otaku, caring for his seemingly average and clingy younger sister, Rina. While Rui openly loves anime and games, Rina acts like a total "normie," hiding a massive secret: she is "Ectiqa," an idolized and mega-famous cosplayer who is completely unrecognizable when in costume and makeup.

The ultimate comedic twist is that Rui is secretly Ectiqa's number one online fan, "Starlight_Knight_01." He donates his part-time job money and sends heartfelt messages of support, having no clue that the cosplay goddess he worships is the same sister he bickers with over breakfast.

The story follows Rui's growing suspicion about Rina's mysterious late-night "job" and the inevitable, hilariously awkward collision of their two worlds. It's a slice-of-life comedy about mistaken identities, secret passions, and a brother's support transforming in the most unexpected way possible.