Arita (有田) is a professional baseball player that Tomohito Sugino admires where he plays for a major league baseball team in New York.
After Tomohito Sugino unsuccessfully attempts to assassinate Korosensei, Korosensei flies to New York to watch a baseball game. It is later discovered that he went to the baseball game in order to get an acute understanding of how Arita's body works in order to help Sugino's pitches.
It is shown that Arita then signed an autograph for Korosensei reading "Damn you, Tentacles!!
- The name Arita means "exist" (有) (ari) and "field, rice paddy" (田) (ta).