Ginga ni Hitori Nobara no Kimi

Junpei has left his hometown where the stars are beautiful at night for the city of Tokyo. Although the bustling city tires him out, he currently lives his life happily with Akira, the caretaker of the share house that he currently lives in. After falling in love at first sight with Akira, Junpei had immediately asked him out and they are now dating. But one day, Junpei learned a shocking truth about Akira... and that is the latter is actually an android!

(Source: Gentosha Comics, translated)