The first five games in the Touhou series. These games were originally released for the NEC PC-9801 computer, while later games were released for Windows.
The Touhou series can be divided into two eras: the PC-98 era, and the Windows era. In the PC-98 era the world was less well defined, and only a handful of PC-98 characters (Reimu, Marisa, Alice, and Yuuka) appear in later games. The Windows era can be considered a soft reboot of the series. Despite this, the PC-98 era is not considered non-canonical.