Ushio's face was becoming very close to inventing new shades of "embarrassed red" at this point. Trying to say 'mistress' was a difficult hurdle, and Hiromi's teasing enquiries were not making it easier. Still fumbling over her words, the bashful could do little more than avert her eyes and try to regain control of her speech. Preferably before too many people took notice of her discomfort.

"No-no-nothing's wrong! I'm pe-perfectly fine!" she finally managed to blurt out, in a shamefully high-pitched squeak. Clamping her lips shut for a moment, she quietly shook her head and continued, "I-I don't need to rest... um, l-let's go now?"
the longer she stayed in one place, the more Ushio felt that the remaining students were looking at her. She didn't want any more embarrassment at the moment.