Cross Days is a Japanese erotic visual novel developed by 0verflow, released on March 19, 2010 for Windows and later ported as a DVD game and for the PlayStation Portable (PSP).

The story, a dramatic slice-of-life, follows the life of Yuuki Ashikaga, a high school student who becomes the ambivalent love-interest of two girls during his second term, and the effects this has on himself and his relationships with other characters.

In the weeks following this, after it was illegally found on peer-to-peer (P2P) networks, a trojan horse disguised as the game was released, publishing the personal information of unknowing users online for public access.

[1] These choices are intricately linked to alternating routes of plot, moderately changing the direction of the story as each is made, ultimately leading to erotic scenes between characters and one of various endings.

Yuuki Ashikaga is a high school freshman in his second semester at the fictional Sakakino Academy, who from his regular visits to the library, grows enamored by Kotonoha Katsura, a classmate who also comes to read.

Though unaware of each other, the girls in question constitute the premise of the game: Kotonoha Katsura, a character well known throughout the franchise as the pivotal love-interest of Makoto Itou, and Roka Kitsuregawa, a newcomer whose efforts to make Yuuki jealous only serve to further complicate her relationship with him.

AiCherry, an interactive movie developer, re-released Cross Days as a DVD game on April 28, 2011,[2] as did PalaceGame, a UMD publisher, for the PlayStation Portable (PSP) on July 29, 2011.

[29] Users tricked into installing the virus, termed a form of "ransomware" in the report, were asked for personal information and then had all of their web history posted to a blog, operated by shell corporation Romancing Inc., for public access.

[29] Cross Days for Windows premiered as the third most sold game on Getchu.com, a major redistributor of visual novel and domestic anime products, during the month of its release,[31] ranking twelfth for the first half of 2010,[32] and thirty-first for the whole year.

The first of these was a strategy guide and artwork book by Junji Goto, character artist for 0verflow, titled Cross Days Visual Fanbook (ビジュアル・ファンブック, Vijuaru Fanbukku) and published by Kinema Junpousha in August 2010.

[39] The subsequent three releases were light novels by different authors but whose cover art was drawn by Goto and illustrated by Jet Yowatari; each book retold the story of the game.

[45] The album contains all of the game's background music, all of which was composed by HIKO of KIRIKO/HIKO Sound, and theme songs performed by Yozuca*, iyuna, Ceui, Kotaro Odaka and Riryka, totaling 25 tracks.

The limited edition of the visual novel came with a figurine of the Kotonoha character,[47] and 0verflow and its partners also sold wall scrolls[48] and Zippo lighters,[49] as well as shower curtains, cushion mousepads, dakimakura cases.