Monster Park ~Bakemono ni Miirareshi Hime~ (jap) by Delta - Adult Sex Game

In the land of Gatoria Kingdom, Marion, a prince, is interested in rare kinds of creatures called monsters. One day, he meets Stia, a princess in a neighboring country, in his country and he wants to see Stia having sex with ugly and violent monsters. On the day Stia comes back to her country, Marion intentionally leads her to the forest where monsters live. At the same time, Iris, Marion's younger sister, accidentally gets lost in the forest....