Imagine:
Harry: We are best friends right?
(Y/N): Yess!!
Harry: So Best friends can keep each others secrets right?
(Y/N): Yup! But why?
Harry: Listen I'll tell you one of mine.
(Y/N): Yeah!
Harry: I'm in love with my best friend.
(Y/N) Takes 10 mins to take that in and then jumps and hugs Harry and Harry puts his arms around her.
(Y/N): *whispers in his ear* I love you to Haz ❤