Satomi Yuuki, a high school boy, stops by his friend's house on his way home from school. He came over to study for a test, but he's instantly intimidated by his friend's older sister. With her flashy hair, glittering nails, and tons of piercings, she looks seriously scary.

However, she ends up making him Calpis, saying, "Gotta have sugar if you're gonna study," and even serves him handmade curry for dinner. One way or another, the sister keeps looking out for him.

This is a story depicting a pure-hearted teenage boy being constantly flustered by his friend's "Scary But Nice" older sister.