|Name (kanji/kana):||鮫島 力|
|Localized Name(s)|| Jack|
Riki Samejima (鮫島 力, Samejima Riki) is the guardian of Hanazono High School and the second most recurring character in Kunio-kun series. He first appears in Nekketsu Kōha Kunio-kun as the first stage boss. He is an eternal rival of Kunio.
- In Renegade, Riki is known as Jack.
- In NES version of Super Dodge Ball, he is also known as Jack, a captain of Team Pro All-Star.
- In River City Ransom, Riki was name Ryan.
- In Crash 'n the Boys: Street Challenge, Riki was named Crush, a member of Team Thornley, who replaces a black character named Raphael.
- In River City Ransom Underground Ryan's full name was Ryan Samejima.
- Riki has a two girlfriends, the one is Mami from Downtown Nekketsu series, while other one is Kyoko from Kunio-tachi no Banka.
- The character Kazuma Kuwabara from the anime Yu Yu Hakusho bares a resemblance to him especially his hairstyle.
- Riki's birthday is on May 5.