A crossover with a magical girl anime could be really fun. Picture the monster girls from Monster Girl Quest getting mixed up with the magical girls. There could be a misunderstanding at first, with the magical girls thinking the monster girls are villains. But then they realize they can work together to fight a common evil. Maybe the transformation sequences of the magical girls could influence the way the monster girls show their powers in new and interesting ways.
How about a crossover with a post - apocalyptic game? The monster girls would have to survive in a desolate world. They might encounter new types of enemies that are a result of the apocalypse, like mutated creatures. And they could also meet survivors who are both scared and intrigued by the monster girls. This would lead to some interesting character dynamics and plot developments as they try to find a new place to call home in this harsh new world.
One idea could be a crossover with a popular fantasy RPG. The protagonist from Monster Girl Quest could find themselves in a world filled with different races and magic systems from the other game. They'd have to adapt and maybe form alliances with new characters. For example, if it was a crossover with 'The Elder Scrolls', the monster girls could interact with the various guilds in Skyrim, like the Thieves Guild or the College of Winterhold.
One idea could be to create an OC who is a half - human, half - monster girl trying to find her place in a world that fears her kind. She could go on a journey to prove that she's not a threat.
One idea could be a quest where the main character has to rescue a monster girl who has unique magical abilities that are crucial to the wizarding world. Maybe she can communicate with magical creatures in a way no one else can, and dark forces want to use her for evil. So the protagonist teams up with his Hogwarts friends to find and protect her.
One idea could be that Ben Tennyson finds himself in a parallel dimension where the Omnitrix has transformed all the female characters into monster girls. He has to figure out how to change them back while also dealing with the new powers and personalities of these monster girls. Another plot could involve a group of evil forces trying to use the monster girl situation to take over the world, and Ben has to team up with some of the friendly monster girls to stop them.
One idea could be a crossover with a fantasy adventure game. The Monmusu characters could find themselves in a new world filled with different races and magic systems. They might have to adapt to new rules and form alliances to survive.
One idea could be a quest where the main character has to rescue a monster girl who is being wrongly persecuted in the wizarding world. Maybe she has a unique power that the dark wizards want to use for evil, and the protagonist, inspired by Harry Potter's courage, sets out to protect her.
Another great storyline could involve a slime girl in the Monster Girl Quest fanfic. Maybe she discovers a unique power within herself that allows her to transform into different forms, and she uses this power to help the other monster girls and humans co - exist peacefully. For example, she could transform into a bridge to help humans cross a dangerous ravine in the monster - dominated land.
In a crossover with 'Pokemon', characters like Ash and Pikachu could be great inclusions. Ash's experience with different creatures could be put to the test when dealing with the monster girls. Pikachu's electric attacks could also create some interesting interactions with the monster girls' unique abilities.
One idea could be a Naruto character getting lost in a forest inhabited by monster girls. For example, Naruto himself stumbles upon a village of cat - like monster girls who initially see him as a threat but later come to understand his good nature. Another could be a story where a monster girl becomes a ninja in the Hidden Leaf Village, facing discrimination at first but then proving herself through her unique abilities.
One idea could be that the mummy monster girl is an ancient protector of a hidden tomb. A young archaeologist stumbles upon the tomb and accidentally awakens her. She initially sees him as a threat but then realizes he has a pure heart. They form an unlikely alliance to protect the tomb from those who would loot it for evil purposes.
You could write a fanfiction about a monster girl oc who is an outcast in her own kind's society. Maybe she has a unique power or appearance that makes the others shun her. A human befriends her and together they embark on a journey to prove that she is not a danger but rather an asset to both the monster girl world and the human world. This would involve a lot of character development and exploration of themes like acceptance and prejudice.