Sugar Glaze Darling

Keiichiro, who is actually the object of Reo's unrequited love, mistakes Reo for a girl and confesses to him. When Keiichiro admits to being bad at dealing with girls, Reo suggests that Keiichiro practice with him, while thinking of him as a girl... An impatient, fiery love story, as sweet as sugar, between a devilish, pampered boy and a straight-laced, super sweetheart.

(Source: Kadokawa, translated)