fit in
phrasal verb.to feel like you belong in a group because you are similar to the other people.
phrasal verb.to be socially compatible with other members of a group; to conform to the standards or expectations of a specific social environment.
“He tried hard to fit in at his new school.”
“It took a few months, but she finally feels like she fits in with her colleagues.”
“The architect designed the modern extension to fit in with the traditional aesthetic of the surrounding Victorian neighborhood.”
often used with the preposition 'with' when followed by an object.
contrast with 'belong', which is more about a deep emotional connection, whereas 'fit in' often implies adjusting one's behavior to match a group.
when 'fit in' has a social object, the preposition 'with' is usually required.