Chummer resembles an anthropomorphic shark with leafy greens in both his mouth and hand.
Chummer can make children loiter after school, then later he will devour them. In the anime, however, instead of eating children, he simply makes kids loiter so that magic weeds appear and he eats them. In the manga, he operates similarly to the manga, only instead of creating magic weeds, he makes the inspirited pull up weeds to eat them due to not being able to pull weeds up fast enough himself.
Chummer appears in the Springdale Underground Waterway. The easiest way to reach the area they are located if you've never been to the Springdale Underground Waterway before is to enter through the drainage pipe located on the western side of Uptown Springdale just near the canal.
Befriended (Yo-Kai Watch): "Of all the chum I've chomped on, you're the chummiest!"
Befriended (Yo-kai Watch 2): "Of all the chum I've chomped on, you're the chummiest!"
Receiving food (favourite): "Really good!"
Receiving food (normal): "Huh..."
Receiving food (disliked): "Why me?!"
Freed from Crank-a-kai: "Free at last! Wanna be...chums?"
"Michikusame" is a portmanteau of michikusa ("loitering, fooling around", literally written as "roadside grass" as grassy roadsides are the archetypal spot for that sort of activity) and same ("shark").
"Chummer" is based on the word chum, which can mean "friend" or refer to a mixture of fish guts and blood, which is then scattered over water to attract sharks in a practice known as "chumming".
Ironically, despite being depicted as an omnivorous Yo-kai, because Chummer's favorite foods are Vegetables in the games, he hates meat.