Youhei is a Japanese teenager who is bored with his life, unable to find excitement anywhere. Even sexual escapades with various women don't satisfy him: he craves for real adventures. But on that particular day, his wishes were fulfilled in a very unexpected way. He was talking to a schoolmate named Mahiro, a girl he didn't even like particularly, when something like an earthquake shattered the school. Youhei and Mahiro hurried to the nearby classroom, only to find a strange mirror-like object - which in fact was a portal to a dungeon in another world. Now the two teenagers have to find a way to escape from the dungeon - and eventually to return home.

Crystal Rinal is an adult dungeon crawler along the lines of Words Worth or Raidy games; but instead of a lonely hero/heroine, the player controls a party of two, Youhei and Mahiro, who fight randomly appearing monsters in turn-based combat. There is also a "talk" command that lets the two heroes chat with each other and comment on the situation. Some gameplay segments follow the template of a Japanese adventure, with menu-based commands and multiple choices during dialogues.

[From Moby Games]