Goshujinsama wa Ouji ga Osuki

Kiryuu Yoshitsugu, like the predecessors of his family, serves the Saoinji family as a butler and is the primary ward over the household’s first and only son, Kaede. Yoshitsugu has held feelings for his master ever since they were children, however, his master wanted a prince - someone he could never be. He has resolved to at least act as his master’s knight and keep his feelings a secret while his master goes on to find his ideal. But can Yoshitsugu really keep himself in check when his master comes running back saying that he’s met the prince he’s been looking for?

(Source: Fujoshi Undercover)