21-Two One- is a Japanese murder mystery visual novel developed by BasiL, it was first released as an adult PC game for Microsoft Windows on May 25, 2001. 21-Two One- was later released for the Dreamcast by PrincessSoft on December 27, 2001. The game is the second installment by BasiL, and after the completion of 21-Two One-, BasiL went on to create their third and final eroge, Cherry Petals Fall Like Teardrops, before forming a new company called Navel. The story follows a young man called Takuya Kirishima, who is a talented surgeon and works in a hospital with his childhood friend Seri Sakaki, however, one day a murder is committed at the hospital, and Takuya tries to solve the mystery. Gameplay in 21-Two One- offers branching plot lines, and a multi-choice navigation, where the player c