Willow

Willow is the titular character from Demonpact: Willow, a spinoff game that isn't finished yet. She can be recruited by using a secret code found within Demonpact: Willow.

Her quirk in battle is applying random effects with the Trick or Treat skills, with Treat buffing the party and Trick hurting the enemy. Unfortunately, the skills behave identically due to a mistake that Goiaba made. Oops.

The game itself describes her as:

"Straight from Demonpact: Willow!! You shouldn't be able to read this."