Minamino Nanami

Ojousama who suddenly moved into house next to the protagonist's. She's one year younger.
She came back from America, and she calls Yuu her "oniichan", claiming that she knows him from childhood, but he doesn't remember anything.
She acts very bright around Yuu, waving her blonde twin-tails and emitting love beams, playing a role of the cute little sister-like character, but whenever any other girl gets close to Yuu, she gets very hostile, and transforms into a ferocious monster.
She has a speech quirk of making "Kyuun!" sound effect whenever she's worried or embarrased.
By the way Modern and Classical Japanese are her bane at school.