Her top got caught

Just as Mikan reached out to grab her missing bottoms, she felt a sudden tug at her chest, stopping her in place. Confused as to what happened, the bottomless girl put her head under the water and saw that some broken branches that had sunk beneath the river had hooked themselves around the string of her bikini top.

"Let go!" Mikan's hands rushed towards the branch and struggled to get the string free. Though it was more accurate to say they fumbled to get them free, between her bikini bottoms drifting further and further away, and that her bra had broken when she was changing, Mikan didn't want this to rip her top too, but she also didn't want to lose her bottoms either.

With each struggle to break her bikini top free, Mikan felt her breasts move around, her nipples breaking free of the top and being exposed to the elements. The water rushing past her nipples started to stimulate them again, and so soon after Ibuki had made Mikan's body her plaything.

The embarrassment of the situation was getting too much for Mikan. At this point, she wanted out of this situation as fast as humanly possible.