"Onegai Teacher" is a 12-episode anime series that blends elements of romance, science fiction, and slice-of-life genres. The story centers on Kei Kusanagi, a high school student who suffers from a rare condition called "Hibernation Syndrome," causing him to fall into comatose states for extended periods. Due to his condition, Kei is socially isolated and struggles to connect with his peers. His life takes an unexpected turn when Mizuho Kazami, a mysterious and beautiful woman, moves into his rural town. Mizuho is revealed to be an alien sent to Earth on an observational mission, posing as a teacher at Kei's school.

The narrative unfolds as Kei accidentally discovers Mizuho's true identity during one of her missions. To prevent him from exposing her secret, Mizuho proposes a marriage of convenience, which Kei reluctantly agrees to. Despite the unconventional arrangement, their relationship gradually deepens as they navigate the challenges of keeping Mizuho's alien identity hidden while dealing with the complexities of their feelings for each other. The series explores themes of love, trust, and the struggle to find belonging, as both characters confront their personal insecurities and societal expectations.

Supporting characters include Kei's childhood friend, Ichigo Morino, who harbors unrequited feelings for him, and Mizuho's fellow alien, Koishi Herikawa, who provides comic relief and occasional insight into Mizuho's past. The story balances lighthearted moments with emotional depth, particularly in its portrayal of Kei's growth as he learns to overcome his fear of forming connections and Mizuho's journey in understanding human emotions. The series concludes with a focus on the evolving bond between Kei and Mizuho, leaving their future open-ended but hopeful.