Dōsei(同棲, lit. Cohabitation) is a Japanese adult social simulation game developed by Tactics, a brand of the joint company Nexton, and first released on May 23, 1997, the same day as the famous To Heart by Leaf. The game was initially playable on the PC as a CD-ROM on the Windows 95 operating system, but was later re-released compatible for Windows 95/98 on September 14, 2000 under the title Dōsei Memorial Collection. The gameplay in Dōsei follows a plot line which offers pre-determined scenarios with courses of interaction, and focuses on the appeal of the sole female main character Manami Minase. The player assumes the role of the protagonist named Masaki Yamada who is living with Manami shortly after they have graduated from high school. Masaki earns money at a job, and when he returns