Eden no Uragawa

Akiba is indebted to a man named Arimura for giving him work, and so is obliged to take in Ikumi, who appears to be the ostensibly-straight Arimura's lover. However, he isn't even told when Ikumi will go back to Arimura. Though initially annoyed by the troublesome situation he's become tangled up in, Akiba slowly finds himself being won over by Ikumi’s pleasant, easy-going nature.

(Source: Oakla Shuppan, translated)