Using Yo-Kai Medals, gained from befriending Yo-Kai, the PC can also summon their Yo-Kai friends to battle other Yo-Kai who are causing trouble in the neighborhood. The Yo-Kai Watch enables the player character to see other Yo-Kai by shining a light on them. When they open a capsule from the machine, they release a Yo-Kai called Whisper, who becomes their ghost butler out of gratitude for his freedom and gives them the titular Yo-Kai Watch. The game series, which remains the flagship product of the franchise, is about a fifth-grader (with the player's choice of a boy or girl, although the rest of the franchise leans on the boy as being canon) who finds a capsule machine in the woods while looking for bugs one day. More overall information can be found here.
After the original video game came out in July 2013, Yo-Kai Watch took over Japan, with an anime, sequel video games released while the original was still selling well, a Collectible Card Game, a collectible card game that ties into an arcade game, multiple different manga, and merchandise out the wazoo, including the titular Yo-Kai Watch and all the collectibles that go with it so kids can pretend to summon the over 400 different Yo-Kai.
Yo-Kai Watch is a multimedia Mon series by Level-5.