i like to think that at some point ladybug gets a lil self concious because she cant really fight and she always has to depend on Chat Noir for that, which isnt bad, but she feels like she is falling behind him, and she wants to stay at his level.
and this leads me to: Adrien and Marinette fencing together.
Imagine him trying to teach her footwork, and technique and he is always super encouraging, even though she really isnt picking up on it as fast as other students
and when she is proud of something, she will show Chat Noir. And he always chuckles at her, because she has her technique all wrong, so then he helps her and shows her a little bit
and during this, he is looking at the novice techniques of ladybug and marinette and realizing they are strikingly similar