What’s this 'justice'?

Surely it's not magic, Mia thought. If her sister could do magic, or witchcraft, or whatever this is, she would know about it by now. However, clearly, somebody sent her a text that can **** her feet, and that's not normal. She examined the first message from the mystery sender.

Is justice a person? She spoke to her phone quietly from her chair in the corner of the café, "How are you doing this?"

A message appeared on the screen.

justice: “You had your chance to apologise! If you feel wronged, you can check out our app.”

"You can hear me! Who are you?!"

The message disappeared before being replaced by the same message. There was a button to open an app.

justice “You had your chance to apologise! If you feel wronged, you can check out our app.”

Useless! Mia slammed her phone on the table, frustrated.

justice “You had your chance to apologise! If you feel wronged, you can check out our app.”

Starting to panic, Mia tried to reason with it, “Come on. I didn’t do anything to you. Let me out of these or I’ll tell the world about you and your stupid app”

'Justice' didn’t reply immediately this time. She figured that the threat of exposing them (even though she hadn't figured out how she would do it) was enough to get some control of her situation back. But then:

justice “you talk too much”

Mia moaned in exasperation and threw her phone down onto the café table. Just as she did, though, she felt an unexpected and unwelcome vibration between her legs.

“What was tha–,“ she started to speak before the vibration happened again, catching her off guard. She impulsively covered her mouth and paused.

A few experiments later, she started to notice that the vibration was something to do with her voice. It seemed to be resonating down her back and between her legs and in a viciously pleasant way.

At least, it would be pleasant she wasn't involuntarily stimulating herself in a café, miles away from her home and unable to walk far (or possibly even stand). She squeezed her cup, trying to relax from the unexpected pleasure.

With no options left, she decided to download the app mentioned in the message. After opening it, flicking past a tens of pages of terms and conditions, and picking a password, finds that all the app seems to do is show a gray background and countdown. Just under 24 hours remained.

... and no quit button. There was no way to even text Lina to ask what was going on.

Her uncomfortable, uncoordinated, but at least stylish walk back to her sister’s dorm was enough of an ordeal that it almost kept her mind from wondering what happens when the countdown hits zero.