Kantōball is a
pokéball regionball of Japanball.
In the Kantō regionball is located the capital of Japanball, Tokyoball.
He's drawn as an eastern Polandball, with a special belt on the partition line which makes it a Pokéball with Asian eyes.
He's good for catching Pokémon!
Kantōball was officaly born as a 1ball, then unified into the Japanese Empireball, and then Japanball.