Kouhei was the one who had asked Rui to do this, after all, and he couldn't pretend that the consequences had nothing to do with him.
"Rui is currently in a state where time continues moving for the rest of us, but it doesn't move for her," Yuka explained, trying to put the situation into words. "That means that when she finally deactivates her ability, it'll feel as though she was just standing there and blinked her eyes for a moment. She won't even need to change her clothes, because the effect extends to everything associated with her, including the bacteria on her body. Basically, as long as nobody interferes with her, she'll remain completely frozen in place. Days, weeks, or even months could pass for the rest of us, but from her perspective, none of that time would have passed at all."
In other words, Rui could effectively skip the passage of time while remaining in the exact condition she had been in when she activated her ability.
