An adult PC game by Hook, released in July 2005. A non-adult version for the PS2 was released by GN Software in 2006.　The game was adapted into light novels, drama CDs, and an OVA.

h4.External links

* Official site (PC): http://www.hook-net.jp/_summer/ 
* Official site (PS2): [s]h[/s][s]ttp://www.goodnavigate.com/GN/products/_summer/index.html[/s] (Dead link)
* Official site (Anime): http://anime.softgarage.com/_summer/
* Official site (Drama CD series): http://www.marine-e.co.jp/sakuhin/_summer/
* Wikipedia: "Underbar Summer":http://en.wikipedia.org/wiki/Underbar_Summer
* VNDB: "Underbar Summer":http://vndb.org/v89
underbar summer