決め込む

きめこむkimekomu

godan verb · transitive

1. to take for granted
2. to assume
3. to be convinced (that)
4. to jump to the conclusion (that)
5. to pretend (to be)
6. to pose (as)
7. to fancy oneself (to be)
8. to feign (e.g. ignorance)

Study it in Yanamino