Mystillion is an AVG (ADV) R18 Otome Adventure Game, set in a western fantasy world. Developed by MagicHouse, this game is a full version licensed game available for Windows. The game has three characters that players can conquer to win their love. The game has 28 still images and can be played with only a mouse.

The game follows the story of Isla, the sole survivor of the "Red Village Tragedy" incident, who was taken in by the Selo Orphanage and now lives on the outskirts of the town. The game has three main characters: Noin, a demon hunter who appears before the protagonist; Ille Coronum, a demon who broke into Aira's house and is interested in the main character; and Raphiel Geri, a young man who is an apprentice priest at the church and has always been watching over Isla. The player becomes the main character and chooses their own destiny, bringing happiness to their beloved and many others.

Please note that this game includes elements of sexual activity and disagreeable sex, contains nudity or sexual content, and has depictions of drugs and alcohol. It also contains explicit or fresh adult sexual content.