Thorn sins, on this game the main heroine can get pregnant every time an enemy cums inside her, after getting pregnant you can still keep playing normally until eventually she gives birth, there are 3 birth scenes(Egg, parasite and goblin). Her children will become allies and they will have specific abilities depending on which enemy impregnanted the heroine.
If the heroine gives birth to a parasite, it will become a flying monster and will attack the heroine.