Ouji na Hime to Hime na Boku

Tori, the son of a poor aristocrat, is on his way home from work when he comes across a woman being attacked by thugs. He tries to help, but it was a sting operation, and the woman bravely fights off the thugs while protecting Tori instead. He blushes, saying, “It's pathetic to just be protected...!" The story begins when Tori is recruited to be the dorm attendant at the Royal Academy, where he ends up working a woman's dorm, where his protector the princess resides.

(Source: Natalie, translated)