Juujirou Oni is a High Schooler first shown in New Prince Of Tennis and amongst the best Japanese school tennis players shown in the series. He is known as The Gatekeeper from Hell.
Oni is seen in the U-17 camp in the 5th Court, sharing in common with Irie Kanata the fact that they are in lower courts than than their actual skill level. Despite being in 5th Court, the members of the 1st Court comment on how powerful he and Irie are who is in the 3rd Court.
