Kawaii dake ja Nai Shikimori-san

The ultimate "heartthrob girlfriend" appears! Naturally unlucky high school student Izumi's girlfriend is his classmate Shikimori. She has a beautiful smile and kind personality and always seems happy when she's with Izumi. She's a pretty, cute, and loving girlfriend, but when Izumi's in trouble… she transforms into a super cool "heartthrob girlfriend!" The fun lives of the cute and cool Shikimori, Izumi, and their good friends never end!

(Source: Crunchyroll)