Extremely loyal to The Boss, to the point he and the other Cross-Eyes who worked with created a wax statue of him to worship. After several failed intents to recreate the research of black powder, his mind became twisted along with his body, becoming a Frankenstein-looking freak like the rest of his companions.
After The Boss disappearance he was instructed by the Top Officers to continue his research of Black Powder, knowing they'll soon run out of their primary product to sell. Him, Hiratsuka and some other members studied the Magic User's anatomy, using the abandoned cabin of Haru as a hideout, in order to understand how to recreate black powder and also fight them back, cutting their smoke vessels and destroying the organs that produce smoke to render them defenseless, when they got no more bodies to test their research, they started to use their own, loosing their sanity in the process.
Prof. Kasukabe, 13, Dr. Vaux and Jonson went to the Hydra Forest to find Kasukabe's wife, to they shock the found Kento and the other disfigured Cross-Eyes in her cabin, soon they attacked the scared humans, but Jonson was able to fight them back, and even kill Hiratsuka, Kento commanded one of his men to pursue the humans as him and the other three took care of the giant cockroach.
Later he engage in a fight with Noi, thanks to their training in hand to hand combat and study of the Magic User anatomy, they quickly overpowered her and used her body as a bargain to heavily wound Shin when the cleaner came to rescue everybody.
Once Noi woke up and killed the last of his men, knowing he would be killed soon, took an extremely rare magic smoke they got in thy research to morph into a grotesque giant, chomped Noi upped body in front of an enraged Shin who used his hammed to carve the Cross-Eyes face to release his partner from the giant. When the fight escalated to the point Kento destroyed the whole cabin just by walking in it, shin, along with the humans, Jonson and the still unconscious Noi escaped from it, before it burn to the ground thanks to some candles near highly flammable stuff along with Kento, his last words while crying were: "Boss... Please come back to us... Soon". His body was found by Tetsujo and Dokuga next morning after the heard the news about the destruction of one of his last hideouts.