is a story mainly revolving around a tight-knit group of friends in high school and how they cope with several life-changing events that are never too far off from intimate relationships.

The main character is a boy named Kei Kusanagi who suffers from a very rare disease which causes a comatose state referred to as a "standstill" whenever he is under severe emotional distress.

After recovering, he quietly moved away from home in order to avoid social difficulty due to his long absence, and began living with his uncle, a medical doctor, and aunt.

The story begins with Kei suffering a minor 'standstill' while in the vicinity of the lake, witnessing several unexplainable phenomena happening there, and then watching as a beautiful half-human alien named Mizuho Kazami materialize beside the shore.

Kazami was sent to observe planet Earth by a seemingly benevolent Galactic Federation in order to prevent humans from making developmental mistakes.

During assisting her in moving in, Kei suffers another standstill, and while in a weakened state explains his predicament to the compassionate Mizuho, who ends up revealing her own origins and purpose on Earth.

The remainder of the series concerns the budding intimate relationships between the close friends, one of whom (Koishi Herikawa) is romantically interested in Kei, and another (Ichigo Morino) who has suffered even greater loss of time from the same disease as he has; the problems of having to maintain the secrecy of the marriage; an interfering parent and sibling visiting from the Galaxy Federation; and Kei learning to overcome the ever-present threat of another lengthy 'standstill' stealing more of his life, particularly as he has fallen deeply in love with Mizuho and desperately wants to remain with her.

anime series, authored and scripted by Yōsuke Kuroda, directed by Yasunori Ide,[5] and produced by Bandai Visual, Studio Orphee and Daume, originally premiered in Japan on the satellite television network WOWOW, between January 10 and March 28, 2002, spanning a total of thirteen episodes, including twelve originally premiering on television plus an OVA episode concluding the series, released on DVD on October 25, 2002.

The manga has since been licensed for North American distribution by ComicsOne and in Brazil by Editora JBC, under the title Onegai Teacher.

The story maintains the basic plot, but adds comic humor that suits the manga format well, taking full advantage of still frames.

However, there are quite a few minor details that have been omitted from the anime or were completely changed: the relationship between Hyosuke and Kaede is deflected, with Hyosuke ending up with Ichigo; Yamada is never introduced; Minoru is much more overt with his lecherousness, but is a great deal of help in Kei and Mizuho's relationship; Koishi's role is diminished somewhat; Hatsuho is only shown in only two frames, as a transmission call to the couple warning them of Maho's wrath and in the other world when Kei has a standstill; and finally, the Okinawan honeymoon is never shown or mentioned.

The light novel version entitled Onegai Teacher: Mizuho and Kei's Milky Diary was written by Gō Zappa and illustrated by Taraku Uon and Hiroaki Gōda.

Martin ultimately concludes that "it is a mildly entertaining series with occasional strong points and some storytelling aspects which offer a different feel than most current romantic fare.