The Prince of Tennis

OVA 4: Kikumaru All Alone (8x4)

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OVA Series: The Nationals Arc Kikumaru plays Singles 2 against Kai from Higa. During the game, it is shown how hard Kikumaru had trained to raise his stamina. His lateral movement has improved so much that it looks like there are two Kikumarus. This motion is called Seal Step, and it looks as if he has a doppleganger.