Rinku was a decent character on the show. We first see him as the first enemy during the Dark Tournament
Kuwabara was his opponent.
Despite his training with Kurama, Kuwabara was struggling hard.
As the yo-yos were too difficult to counter.
Luckily, his spirit sword was now bendable.
The fight almost ends in a draw, but Rinku gets back to the ring in time.
While Kuwabara wastes his time yelling at an unconscious Yusuke Urameshi.
He comes back during the Three Kings saga. First agreeing to fight for Yomi, and then joining the Demon World tournament.