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.... The forest is full of dangers... There are many monsters that can be called natural enemies of humans. Even though the two princesses were her virgins, the cloudy seed juice of the hideous monster is poured into their defenseless and innocent bodies. Her clothes are torn, her belly is bulging, and monster seed juice is constantly flowing from her crotch. A male flocking to a beautiful body! Male! Male!! The monsters who forcibly enter, are poured out, sometimes devoured, and while running around the forest, he notices an abnormality in his own body... and...!!!!!! A beautiful princess who is tossed by the intense pleasure, her eyes widen, and continues to orgasm like crazy... Will the two princesses be able to return to the castle safely? This work depicts beautiful princesses lost in a dangerous forest who are relentlessly targeted by cruel monsters, the natural enemies of humans, trying to return to the castle while being pursued. It's an "ecosystem heterogeneous erotic work". In order to realize straight and surprising content that is different from the existing erotic development, we replaced the "animals that are preyed" that appear in programs such as "The Law of Nature" with humans, and the existence of being hunted. I'm going to draw "human". The reason why monsters attack people, how they do it, coexistence with other creatures, and the "forest ecosystem" monsters' ecology, where the common sense of those humans does not apply at all, are realistically set. If there are creatures that inject seeds or lay eggs, there are also creatures that they target in order to eat them... The heroines continue to be helplessly devoured by such creatures. "Erotic" as "action to live", not just erotic, is a novel content that has not been seen in Delta's work so far. In this work, the grotesque appearance of monsters, which is the biggest selling point of heterogeneous eroticism, is set in detail and visualized, and more than 20 monsters will expose their appearance and attack the heroine! A noble princess knight and a cute sister princess expose their faces over and over again and get excited! The familiar “continuous climax, ahegao” in “Reika” and “Keeping” is still alive in this work!