Suki tte Ienakute Shinu!

Akari, a negative, gloomy introverted high school girl who imagines the worst in any situation, looks forward to meeting her younger brother's friend, Mikage, whom he brings home. She racks her brain to come up with a plan to get close to him in her own gloomy way. An agonizingly cute unrequited love romantic comedy between an extremely gloomy girl and her younger brother's teasing friend.

(Source: Shogakukan, translated)