It hadn't been one big moment, he was sure. Perhaps, it was just a hundred small ones.
Adrien had always been curious to know the identity of the woman who fought alongside him in a red spandex ladybug suit ever since they were teens. He had, over the years, tried his best to finally give a name to the most selfless, clever, and amazing girl he had ever met.
Maybe that is why it came to him so effortlessly.
Her mysterious eyes the exact shade of blue, cue of the deep sea waters, he had gotten lost into, the moment he first saw them. The way she carried herself with such grace and confidence- despite her clumsiness-the kindness and willingness to help each one in need and the demand for justice anytime she saw anyone wronged, were too prominent to be left unnoticed.
Even down to the way she stuck out her tongue when she concentrated. How her eyes sparkled with confidence whenever she figured things out, may it be a design to take over the fashion industry or a way to defeat the Akuma. He had watched her crack the biggest of the Akuma mysteries too many times not to recognize it.
It has just dawned on him, an afternoon sitting at the coffee shop across the table from her, as he saw her giggle at something Luka whispered into her ear. He observed how her dark midnight hair reflected the light that came in through the window and how her eyes shone in the sunlight. She looked eternally beautiful. And the thought landed on his head as a cat lands on its paws.
He smiled sadly from afar as he watched Luka get down on one knee, the ring outshining in all its glory with the Eiffel Tower standing behind them as the sunset forming the most exquisite setting for a proposal. He heard her squeal in delight, shout a "yes" as her initial hysteria and shock washed away. As the guitarist slid the ring into her finger and stood back up, the couple- now engaged- crashed their lips together, all the while shedding happy tears.
Marinette Dupain-Cheng -soon to be Couffaine- didn't love him anymore.