Ima wa Mada "Osananajimi no Imouto" desu kedo.

Synopsis

Touki Futahara is the younger sister of Iori Fuyutsuki's childhood friend and an incoming student at their high school. She's a self-proclaimed little devil and "the girl most envied by seniors." Now she's waiting at Touki's door every morning. "Senpai! Give me your hand! Let's hold hands to stay warm!" But Iori knows that Touki's actually more like a shy puppy who blushes at the slightest touch. All the bold teasing is just an act, and she's feeling nervous inside. (Source: Kadokawa, translated)