Onegai Teacher! (おねがい ティーチャー, Please Teacher!) or Please Teacher! (おねがい☆ティーチャー, Onegai Tīchā, Onegai ☆ Teacher), is a Japanese anime series, directed by Yasunori Ide and written by Yōsuke Kuroda, and produced by Bandai Visual, which was adapted into a manga and light novel.
The Please Teacher! anime series premiered in Japan on the WOWOW satellite television network between January 10 and March 28, 2002, spanning a total of 13 episodes, including twelve originally premiering on television plus an OVA episode released on DVD on October 25, 2002. It was adapted very soon into a manga, serialized in MediaWorks's shōnen manga magazine, Dengeki Daioh, in January 2002, and was also later adapted into a light novel, entitled Onegai Teacher: Mizuho and Kei's Milky Diary, published in March 2003.
There is also a sequel called Please Twins!. In total both series have 26 episodes. 12 TV and bonus OVA.
Kusanagi Kei, a high-school student living with his aunt and uncle, has an encounter with a female alien. This alien is revealed to be a new teacher at his school. Later, he is forced to marry this alien to preserve her secrets. From there, various romantically-inclined problems crop up repeatedly.