Based on @femslash-february's Light prompt of "Token".
"Kagami! I have a gift for you!"
The gift was a choker, with dark silk stringing a small dragon charm, designed to sit close on the throat like the dragon miraculous did.
"It's lovely," Kagami said, studying the charm. Marinette's new interest in metalwork shone through with the delicate craftsmanship. It wasn't perfect, but it was still made with love and care. Longg would love it. "May I ask what inspired you?"
Marinette's cheeks turned pink, which was a strange reaction. "Oh, uh, it's a dumb reason..." She fiddled with her fingers. Kagami waited though, knowing that her dear friend would always eventually tell her. "I was doing some reading about medieval French authors for my Literature class, and they introduced this thing called courtly love to King Arthur." Wait. "And one of the things was that ladies would give, like, little tokens of their support to their favorite knight, usually before a tournament."
Kagami's entire face went hot. "And...?"
"And I was thinking that, hey, Kagami deserves to be cheered on at all of her tournaments, but I can't always make them!" Marinette stopped fiddling and began to instead rock on her heels, her face growing even more red. "So I decided to make a token for you, so that you always know I'm cheering you on, but now that I think about it, I don't think you can wear it with your fencing uniform-"
Marinette reached for it and, in a burst of instinct, Kagami hissed as she protectively pressed the choker to her heart.
Kagami couldn't let her shock stay too long, though.
"No. It's mine now," Kagami clicked the choker around her neck. It sat warm on her skin and she could actually visualize Marinette making it, her loving fingers forming the charm. "You can't take it back. I will wear your token proudly-"
She grabbed Marinette's hand and slid her family's ring off, sliding it onto her finger.
"As long as you wear mine."