One idea could be a monster girl who is a mermaid and she has to adapt to living on land in an everyday human world. Maybe she gets a job at an aquarium and has comical encounters with visitors who don't know she's a real mermaid. Another could be a harpy monster girl trying to fit into a human school, dealing with things like flying in gym class and eating different food from what she's used to in her nest.
A plot could revolve around a lamia (snake - bodied monster girl). She moves into a small apartment in the city. The neighbors are initially scared but as time passes, they realize she's just a normal girl with some unique needs like a warm place to sunbathe. She could start a business selling hand - made snake - skin crafts. This would show her everyday struggles and triumphs in a human - dominated world.