The phrase "fits in with" is often used to describe how well something or someone blends in with a particular group or environment. However, there are many synonyms that can be used to convey the same meaning, including "aligns with", "conforms to", "adheres to", "complies with", "harmonizes with", "matches", "congrues", "corresponds to", "integrates well with", "coincides with", "complements", and "syncs with". Each of these synonyms carries a slightly different connotation, but they all share the same idea of something or someone blending seamlessly into a particular context.