Kakyūsei (下級生, Kakyūsei; lit. "Underclassmates") is a dating sim series by ELF Corporation originally created by Masato Hiruta, as a spin-off of the Dōkyūsei series. Kakyūsei was released on PC-98 in 1996, MS-DOS and Sega Saturn in 1997, Microsoft Windows in 1998 and Mac OS in 2000. A sequel, Kakyūsei 2, wss released for Windows in 2004.

An anime OVA based on the first game, Elf-ban Kakyūsei (エルフ版　下級生, Erufuban Kakyūsei; lit. "Elf Version Underclassmates"), was created by Pink Pineapple in 1998. The title distinguishes the anime from the similarly titled but unrelated OVA series of the same title, Kakyūsei, also produced by Pink Pineapple, but earlier, in 1995. It had a TV series produced in 1999, after the success of the OVA. The 14th episode of the TV series was never aired on television. A television series based on Kakyūsei 2 was also released in 1997, as well as 2006–2007 OVA sequels and spin-offs based on Kakyūsei 2, that were considerably more explicit than the TV version.

The story revolves around Mizuho Yuuki, whose best friend Miko has fallen in love with Tohru. Miko is fairly innocent and comes from a strict background so Mizuho tries not to get in the way of their relationship despite her growing awareness of Tohru who is currently boarding with her family, and accepts going on a date with the wealthy Haruhiko. There is also outside interference from Ai, a younger student in their school, who also likes Tohru.