Banchou Wakusei, The World of Ruy, or Ryu in Another Planet (番長惑星 Banchō wakusei) is the third and final entry in the Ryu Trilogy.
“UFO, flying saucers, I wonder if they do exist? What about Nessie? The Abominable Snowman? Ghosts…? They may exist or they may not. Our world still has mysteries that cannot be explained by modern science, and people can often attribute supernatural nature for things that they can’t understand. But what if there’s a parallel world where all that can be real? There are those who believe in the existence of multiple worlds, at least in theory. It’s not possible to tell for sure, but in the world of this manga, they do exist. So, please, enjoy this new adventure to another planet with Ryu!"
The story starts when Ryu is at disadvantage during a fight against a rival gang of delinquent students. To escape from them, Ryu tries to hide himself in this large tree in a Inari Shrine. There, he finds a tunnel that looks to have no end, he then can see his own shadow and after some strange events, he finds himself back at the same Inari Shrine.
But things are not exactly the same anymore. There are robot policemen patrolling the streets, and they shoot a man right in front of Ryu. Animals like dogs have a totally different aspect than the ones he was used to, and airplanes have the shape of a UFO. During his fall, a massive energy discharge had allowed his physical form to shift through dimensions, taking him to a strange but deceptively similar parallel universe.
All his friends and relatives do exist in this parallel world, but Ryu is unique among them because his other dimension self is now fused with the alternative world Ryu, giving him double the strength, resistance, and speed of a regular human being. These new powers would come in handy after the discovery that this world works under the law of the jungle, where people could get a license to murder without any consequence.
In order to survive in this world, Ryu has to find other people who can rely on, but a mysterious organization called Shadow is after his life and would use any method to get rid of him. In the meantime, Ryu needs to solve the mysteries of the parallel world, which could be connected to the ancient Maya civilization and the Devil’s Triangle.