is a platform game series developed by Telenet Japan. The original game was developed in 1986 for the MSX, and its popularity has spanned four sequels, a spin-off, and remakes across several platforms, notably the TurboGrafx-16 and Sega Mega Drive until the early 1990s, when it was quietly retired. The Mega Drive/Genesis entries were all published in North America by Renovation Products. Later, Telenet sold the series' rights to a company known as Eants, which re-tooled the series as hentai games after Telenet shut down in 2007. The series has formed two mobile games released by Bandai Namco Games in Japan and a manga by Kill Time Communications.