Love Monster (MIO Junta)

From September Scanlations:

Akira’s grown up thinking of his friend Itsuki as something of a little brother—until Itsuki confesses he’s been in love with Akira for years. But while Itsuki is content to keep their relationship the same as it’s always been while he waits for Akira to process the affections he’s just been presented with, Akira finds himself growing increasingly—and inexplicably—irritated with the cool demeanor Itsuki manages to adopt in front of someone he supposedly is in love with.