Otonari-kun wa Kyou mo Watashi wo Komaraseru

Mion, a worry-prone high school girl, finds herself seated next to Houichi—tall, intimidating, and downright scary... or so she thinks. At first, every day is filled with anxiety, but as time goes on, she realizes he's not so scary after all. In fact, he's making her heart race in a whole different way—how troublesome!

(Source: Kodansha, translated)