(K)night & Day: Hirotta Gyaku-Trip Kishi ga "Osu" ni Naru made

Anna picks up Kei, a mysterious knight who has taken a reverse trip to modern Japan. Anna was getting used to strange cohabitation, but the sexual desire she had left over after half a year of masturbation abstinence was already at its limit... The man in front of her is polite but quiet, unfriendly, and stoic. Her curiosity begins to tingle.

(Source: DLsite, translated)