She runs into Adrien.

Turning the corner, Marinette sees Adrien walking down the hall, surprised to see her. She trips, and falls into his arms, her face digging into his chest. She was mesmerized by his scent, even after Adrien put her back on her two feet.

Holding her by her bare petite shoulders, he couldn't help but take a good look at her athletic figure, her under ensemble of a matching hot pink sports bra and boyshort panties with a lace trim around the legs. He couldn't fathom why she was in her underwear, mainly because his brain was more focused on her beautiful body.

"Hide me" was all it took for Adrien to hear to get into action.