From TachiNeko Guild:

Set in post-World War II Japan, this is a story of young Haruomi, an heir of the prominent Morimura family. Stripped of his aristocratic title while facing a repossession of his estate, Haruomi finds himself thrown on the mercy of a wealthy Japanese American, Tsutomu Oshio.

At first, Oshio wants nothing to do with a naïve noble. After all, he hates the Japanese above all else. Yet as the days go by, Oshio finds himself inexplicably drawn to Haruomi’s innocence. Driven by a desire to rid himself of his newfound feelings, Oshio sets it upon himself to disrupt Haruomi’s flawless façade.

Through the hope of saving his bedridden mother’s life, Haruomi accedes to Oshio’s scandalous demands to become his “servant”. Thus, Haruomi’s new life as his master’s plaything begins…

Note: It sounds like the Japanese version of this title included a separate one shot about a host club. While the version published by Enju Group does not.