Monmusu Quest! Origins: Assaulted by the Vamp

Monmusu Quest! Origins: Assaulted by the Vamp is an erotic visual novel with RPG elements. It is the first chapter of the original Monster Girl Quest trilogy. In the land of Ilias, humans are ravaged by monster girls, who prey on men for their essence. Luka, a young hero, has a dream of the goddess Ilias commanding him to slay the monster lord and bring peace to the world. However, Luka believes that peace can instead be achieved through coexistence between human and monster. He then meets a mysterious lamia named Alice and they both decide to set off on a quest for coexistence between the two races.

The game is a visual novel with branching paths as well as RPG combat against a variety of monster girls. The combat is turn-based, and ends when the enemy's health reaches 0 or some puzzle element is solved through a series of specific commands. If Luka's health reaches 0, the fight is failed and a sex scene is played in which the monster girl rapes Luka. All sex scenes can be skipped at will, or replayed from a scene selection in the main menu.

The game's art is drawn by many different Japanese artists with a variety of unique art styles. One of these artists, Kenkou Cross, is the author of the "Monster Girl Encyclopedia" series of books which partially inspired the game. Voice acting is also featured, but only for the main female characters.