[[Yo-criminalcriminals]]s are are NPC [[Yo-kai]] that spawns only on the map. Players do not battle them. To catch them, you simply tries to run into them and mash A, it's also much, much easier to progress the story till you get the [[bike]] to make the chase a joke. You'll know you see one when it runs away from you when you walk randomly around town. You can only catch these once per day, and you need to do it 3 times.
When you catch them three times, the Yokai gives you a random SINGLE letter of the password you need to unlock the rewards. Yes, that means you better work with other people and hope you can assemble all the letters. Additionally, the password can have up to 8 letters.