In the Cosmos Sky) is a Japanese adult visual novel developed by Marron that was released for Windows on July 27, 2001.

The story is told from the perspective of Yasuomi Nīzawa, who discovers more about his childhood memories as the high school cultural festival approaches.

Light novels, a comic anthology and audio dramas have been produced based on Cosmos no Sora ni.

Throughout the game, the player encounters CG artwork at certain points in the story, which take the place of the background art and character sprites.

Throughout gameplay, the player is given multiple options to choose from, and text progression pauses at these points until a choice is made.

[4] The scenario was written solely by Takei Tōka, and most of the game's art was drawn by Kō Iwadate, who was also in charge of character design.

[6] On July 27, 2001, Hobibox released Cosmos no Sora ni as one CD-ROM compatible to the Windows 95/98/ME operating systems.

[7][8] A 305-page light novel adaptation titled Cosmos no Sora ni: Nanazaka no Mon (秋桜の空に 〜奈々坂の門〜, lit.

[10] A self-published light novel titled Himawari no Chapel de Kimi to vs Cosmos no Sora ni (ひまわりのチャペルできみとvs秋桜の空に) was included with the limited edition release of Himawari no Chapel de Kimi to, the third and final visual novel developed by Marron, on August 24, 2007.

Memories to the Sky) by Yukari Tamura (Wakana's voice actress), and "Everlasting Flower" is the ending theme for the third CD.

[23] Cosmos no Sora ni is considered to be a pioneer of the "older sister game" (姉ゲー, anegē) which started to gain popularity in 2003.