Adrien never meant to know, it was an accident really, after he transformed and went out for the first time as Cat Noir, he passed by the bakery and saw from Marinette's room her transformation into Ladybug, he blushed and moved quickly away to hide and swore to himself to never reveal that he knows and to protect her from any danger he finds, when they went back to school after introducing themselves as heroes, Adrien arrived early and left a small box at Marinette's seat.

Inside the box was a bracelet with an apple blossom charm, he left a note saying he was sorry and explained what really happened, he just hoped she would forgive him for the misunderstanding Chloe caused, she ran in and took her seat but he didn't know if she liked the gift… he could only wait for her to talk to him in the end, when the day ended he found her outside looking up to the sky as it rained, he found it a little strange but walked over to find an umbrella in her hand… and the bracelet on her right wrist making him smile "I'm only giving you one chance… let something like that happen again and I will never forgive you" she said before opening her umbrella and walking off.

He could understand her message clearly, no matter what he had to be careful as she won't forgive him next time… even if they were to become friends in the end… but that was enough for him as he decided that no matter what, that as Adrien Agreste or as Cat Noir… he would protect Marinette Dupain-Cheng even when transformed into Ladybug he would protect her from anything, anyone and everything that was a threat to her.

Especially if it's himself…