_Summer (アンダーバーサマー, Andābā Samā, Underbar Summer) is an adult Japanese visual novel developed by Hooksoft which was released on July 15, 2005, playable on the PC as a CD; a PlayStation 2 consumer console port called _Summer## followed on August 24, 2006, by GN Software. An updated version of the original game, called _Summer Renewal Edition (_Summer新装版, _Summer Shinsōban), which is compatible up to Windows Vista and is playable on a PC as a DVD, was released on December 21, 2007.

The gameplay in _Summer follows a plot line which offers pre-determined scenarios with courses of interaction, and focuses on the appeal of the six female main characters. The story revolves around Takumi Kaizu, who after years of making good friends, many of whom are female, is asked by his best male friend Osamu Funada if he likes anyone. With his last summer in high school quickly approaching, Takumi decides to find someone to like by the end of summer vacation. _Summer has had overall well received sales, premiering as the most sold bishōjo game in Japan during the first half of July in 2005, and would go on to chart twice more.