Inaho-kun wa Nise Kanojo no Hazu Nano ni

Shintarou Mori, a first-year high school boy, is teased by his friends for wanting to find a beautiful girlfriend and having a sparkling social life. His classmate Inaho Sawatari is regarded as the smartest and most beautiful girl in school. The two of them shouldn't have anything to do with eacher, but when they're inadvertently mistaken for a couple, Inaho proposes: "How about we pretend we're really dating?" They act like a couple in public, but it turns out the most beautiful girl in the school is actually a very cute boy...!

(Source: Earth Star Entertainment, translated)