Mr. Arthur Rutherford's Very Late First Love

Tokihiro quit his job as a high school teacher due to an incident. While feeling down and not knowing what to do with his time, his friend gets him a job as a Japanese tutor for Arthur, the general manager of an international company. Arthur is extremely handsome and smart, which has Tokihiro's heart racing all the time. Arthur, who is a player and openly gay, says Tokihiro is not his type and seems completely uninterested at first, but...?!

(Source: MangaPlaza)

Note: Includes two extra chapters.