Angels and demons have a disagreement concerning the human race. Some vote for its extermination; other suggest milder solutions. In the end, it is decided to test the humans' abilities. The Earth is invaded by hostile angels and demons of different kind. A boy named Takami is chosen to be the subject of the "examination". At the same time, a young woman named Yuima, discovering her celestial heritage and magical powers, decides to put an end to the invasion...

The player can choose to begin the game as either Takami or Yuima. Takami is a fighter type with strong physical attacks; Yuima is a magic user. Their stories, however, converge early in the game, after which they fight together in a party.

Tenshin Ranma is a traditional first-person 3D dungeon crawler. Enemies appear randomly and must be dealt with in turn-based fashion. Auto-map appears near the main exploration screen, highlighting already explored areas. Leveling up is automatic, like in most Japanese RPGs. Some dungeons have shops, where the heroes can buy weapons and items.

There are scenes with nudity and eroticism, but no "hardcore" pornographic sex scenes.

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