Osaka, Japan (SportsNetwork.com) - Shinsuke Yamanaka retained his WBC bantamweight title Thursday with a seventh-round knockout of previously unbeaten Diego Ricardo Santillan.

Yamanaka dominated the bout, first knocking down the challenger in the sixth round before delivering a left that sent the Argentine to the canvas for good just 36 seconds into the seventh.

It was the eighth successful title defense for Yamanaka, who improved to 23-0-2 with 17 knockouts. He first captured the belt in November 2011 with an 11th-round TKO of Christian Esquivel.

Santillan had won his first 23 fights.