She wasn't sure how long it had been. A year? Three? A life time? She had been with her partner for so long, she couldn't imagine herself with out him. Or rather, Ladybug without him.
However, Marinette can. She had finally took charge, concurred her fears, and spoke to her crush. All with the help of Chat Noir. He supported her and cheered her on the entire time. It was the sweet blissful relationship she respected from him. And yet, he treated her differently as Ladybug when she spoke of her crush-turned-boyfriend.
"Why have him and not me?"
He complained and pouted. Their relation turned a bit sour, but both knew better than to let it interfere with their jobs as heroes. When he spoke with Marinette about it, she knew he was worse when she supported her alter-ego instead of him. Their relationship turned sour as well, but not as much so; knowing her as an innocent civilian must have changed that.
It hurt when Chat slowly quit smirking with Ladybug. It shook her whenever she left remarks open for puns, and he didn't bother to take them. It was terrible when he stopped flirting and chasing her whimsically. She regretting ever telling.
"You have a boyfriend... I'm not a monster, you know."
Her relationship with Adrien was progressing better by the day, and Chat still visited with smiles and laughs. He often wrapped an arm around her and nuzzled with her. She usually needed to remind him that they could only be friends, because of her boyfriend. He never seemed hurt by it. Only smiled brighter than before.
It hurt Ladybug that that he never smiled that way to her. He only did so when their job was done, or when the civilians were all safe, or when he had to hurry and de-transform. Whenever she asked for why he acted that way, he gave her a blunt and vague answer.
"You have someone else in your heart. All we can do is just be friends."
She would frown, wishing he would smile at her like he used to. He had such warmth, but not for her anymore. Yet in her heart, she felt like he would always be immortalized and special. It hurt when he said that answer. He would never look at her the same way again.
However, she knew he was right. It was their fate. Her heart was whole when with Adrien. All she could do when with Chat, is just be his friend.