Koucha Ouji (1997)

Taiko and her friends Haruka and Someko are the only members of their high school’s "tea club." (English, not Japanese, tea.) One night they are drinking tea by moonlight and diminutive princes Assam and Earl Grey emerge from their teacups. They can’t return to their Tea Kingdom until Taiko and Haruka make three wishes each, but the pair are reluctant to wish foolishly, which leads to the Princes of Tea hanging around the human world for a while. Various hijinks ensue, and more about the history of the Princes is revealed until there is enough drama to choke a teakettle with.

Source: www.anisearch.com/manga/4619