Housekishou Richard-shi no Nazo Kantei

One night, a college student with a strong sense of justice, Seigi Nakata, saved a gorgeous foreigner, Richard, who was being harassed by some drunks. When Seigi found out that Richard was a jeweler, he asked for an appraisal on a ring with a shady history; one which his grandmother had kept secret until she died. The appraisal had revealed her past, truth, and desire. It led Seigi to work as a part-time employee for Richard’s jewelry store, the "Jewelry Etranger" in Ginza. While solving various "mysteries", the relationship between Richard and Seigi gradually changes. (Source: Crunchyroll)