Grainpa in Yo-kai Watch 2

Grainpa may appear as a red mailbox Yo-kai Spot. These can appear slightly below-left the Tunnel entrance in Downtown Springdale, at the top of Downtown Springdale in between the Shopper's Row and Uptown Springdale exits, next to the Mirapo at Excellent Tower, or to the left of the Scratch Card Booth outside Excellent Tower. If he's not the Yo-kai in it, don't talk to that Yo-kai, sleep for 4 days, then save and sleep one more day. Then go searching again. You can save once you find Grainpa to continuously fight him until you befriend him normally.

Grainpa rarely also appears on the train.

He can also be freed from the past Crank-a-kai with a Green Coin and from the Ultimate Oni Crank-a-kai.