""Valis, known in Japan as Mugen Senshi Valis (夢幻戦士ヴァリス, Mugen Senshi Varisu?, lit."Valis: The Fantasm Soldier"), is a Japanese platform game series developed by Telenet Japan. The original game was developed in 1986 for the MSX, and its popularity has spanned 4 sequels, a spin-off, and remakes across several platforms, notably the TurboGrafx-16 and Sega Mega Drive until the early 90s, in which it was quietly retired. The Genesis entries were 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 2 Mobile Phone games released by Bandai Namco Games in Japan and a manga by Kill Time Communications.
The Valis games (as they were known in America) tell the story of Yūko Asou (麻生 優子, Asou Yūko?), a schoolgirl in late 1980s Japan who is fated to protect three different realms -- our own Earth, the land of spirits, and Vecanti (ヴェカンティ, Vekanti?), the Dream World -- by wielding a mystical sword known as Valis.""
Source: Wikipedia, "Mugen_Senshi_Valis", available under the CC-BY-SA License.