He's a simple octopus, who has a huge size as a spirit.
He was caught a few years ago, using a Takotsubo, but he jumped off the truck that transported him to an inn as it went through a tunnel. He dried up and a giant spirit manifested, remaining inside the tunnel as he feels it’s a safe place, and attacking anyone trying to go through it.
As the inn association are having a hard time, Rinne and Tsubasa were hired to deal with the problem. And as they confronted him, he got enraged upon seeing a Takotsubo and hearing about Octopus food. In the end, Rokumon dragged the octopus out of the tunnel and Rinne blocks him from fleeing back inside, and his dried-up body is found by Sakura. As soon as they bring the octopus back to the ocean, he comes back to life and sprays Rinne with ink as he swims away.
- A story featuring a Takotsubo is also shown in Ranma ½.