Shin starts out as Kenshiro's friend and rival, trained in the Nanto Seiken style—specifically the Lone Eagle Fist, a technique that lets users pierce flesh with their bare hands. But he's secretly obsessed with Yuria, Kenshiro's girlfriend, and his jealousy eats away at him until Jagi manipulates him into making a move. Shin challenges Ken, beats him, and brutally carves seven scars across his chest in the shape of the Big Dipper to try forcing Yuria's love. It almost works, but even after Yuria gives in, she never really means it. Shin leaves Kenshiro to die in the desert.
Rather than accept that Yuria doesn't actually love him, Shin builds an entire army under the banner of the Bloody Cross and founds a whole city called Southern Cross in her honor. It's obsessive and ultimately pointless—Yuria's heart stays with Kenshiro no matter what Shin does.
When Kenshiro inevitably crawls back out of the desert and tracks Shin down, they have their final confrontation in Southern Cross. Kenshiro kills him with the Cross-Kill technique, leaving Shin's own emblem seared into his chest. Before dying, Shin reveals that Yuria apparently threw herself off a cliff. Unable to face that fate at Kenshiro's hands, he jumps after her.
Ken gives Shin a proper burial afterward, acknowledging that beneath all the cruelty and obsession, Shin was just a guy who loved the same woman he did.
Content compiled by AnimeList.moe from publicly available sources.
