AU from prior to the S4 finale, but most of the middle episodes, presuming that the worst of the conflict will get resolved without any further identity reveals.
"Happy Birthday!"
The words washed over Marinette, her attention distracted. Adrien turned, caught her gaze, and smiled. She flushed and looked away.
"Yo, girl," Alya continued, waving her hand in front of Marinette's face. "At this rate, we'll graduate before you tell him how you feel."
"I'll do it next time, really."
"Seriously, Marinette."
Marinette sighed and let the flash of blonde hair in the corner of her eye stay unmonitored. She scanned the sky above for akumas, a good distraction when she needed it. "I've gotten much better at actually speaking to him."
"You're seventeen now. One year left of school. After you graduate, will you even be near enough to talk?"
The image of Adrien waving goodbye, off to London with his extended family, Spain for photoshoots, or even just moderately outside Paris. Might as well be the moon, with this never ending barrage of akumas from the new Hawkmoth.
"I'd hoped, that after Hawkmoth—" she said quietly, the old doubts from her ill-fated relationship with Luka still haunting her.
"And then ole Mothy passed along the miraculous when you finally cornered him. I still wonder if it's okay not to turn him in."
"As Ladybug? With no proof? Imagine the trial. Anyways, he can't harm anyone now, and it's better for Adrien not to know. Chat is still reeling—he really thought we proved him innocent ages ago, when I was suspicious. I keep telling him it's not his fault."
Alya eyed her and her fingers twitched like she wanted to pull out her notepad and interrogate Marinette into submission. "No changing the subject. If you're going to keep one secret from Adrien, you should tell him the other."
Save me from well-intentioned and usually correct friends, she thought, and then the ground began to shake. Apparently the new Hawkmoth could deliver.