1A very close, trusted friend — a best friend or bosom buddy; conveys deeper closeness than the plain word 「友達」(friend).
小学校からの親友と今でも毎週会っている。
I still meet up every week with my best friend from elementary school.
親友の結婚式でスピーチを頼まれた。
I was asked to give a speech at my best friend's wedding.
親友になら、悩みを何でも話せる。
If it's my best friend, I can talk to them about any worry.
彼とは大学時代からの親友で、今もよく飲みに行く。
He's been my close friend since university, and we still often go out drinking together.