Never

When Hiyoko thought about Mikan, the first word that came to her mind was useless. That added to the fact that if Mikan didn't grab Hiyoko, she wouldn't be stood outside naked made Hiyoko's decision easy.

"Why would I work with you? You're the reason I'm in this mess!" Hiyoko yelled out, clearly not caring about who might hear.

"But I can still help!" Mikan cried out.

At that point, Hiyoko anger boiled over and she slapped Mikan's ass as hard she could, Mikan falling over as she clutched her ass from the pain.

"You want to help me? Then bend over and I'll get out all my frustrations." Hiyoko said as she stomped over to Mikan.

Every step Hiyoko took made Mikan's fear grow immensely.

"I'm sorry!" Mikan said as fast as possible before she stood up and ran even faster, her hands covering her naked breasts in some attempt to hide her nude body as she ran down the corridor.

"Hey get back here!" Hiyoko chased after while not even bothering to cover her body, she wanted Mikan to suffer more than she wanted to cover.