Battle Spirits: Ryuuko no Ken

Martial artist Ryo Sakazaki and his wealthy friend Robert Garcia break into an apartment while chasing a runaway cat, only to stumble upon a murder connected to South Town's criminal underworld. Crime boss Mr. Big becomes convinced that the pair possess the Eye of Sirius, a priceless diamond stolen from him.

Unable to force the gem out of them, Mr. Big kidnaps Ryo's younger sister Yuri. With no diamond to trade and no patience for the gangsters standing in their way, Ryo and Robert fight through South Town to uncover the truth behind the theft and bring Yuri home alive.