Class de Ichiban no Kanojo, Jitsu wa Bocchi no Ore no Kanojo desu

Seiji Shinomiya, a self-described loner who thinks that youth is a pain, and Kotone Kanzaki, an unobtainable flower who has the best grades in their year and is also a model. The two of them, who absolutely never interact in class, have a secret: they are actually secretly going out, and nobody knows it. When this boyfriend who doesn't know how to depend on others and girlfriend who wants to be spoiled are together, they're able to be their true selves. Eating lunch together in the Literature Club room, using the rain as an excuse to have a sleepover date, secretly embracing each other behind the gym... They're distant in class, but when together, they're close.

(Source: Kadokawa, translated)