Lets Recycle (資源を大切に！, Shigen o taisetsu ni!) is the 40th chapter of Dorohedoro.
Back in the place where the restaurant competition took place En wonders where Nikaido is, and collapses in pain while some goons assist him.
In the basement of the devil church Asu explains to Chota about the consequences of having En's contract outside of Nikaido (explaining the boss sudden collapse). The bird mask eagerly asks if putting the contract inside his belly will make him En's partner. The devil explains that it doesn't work like that - he needs to exchange his own contract with En to become his partner, and to do that, he needs Chidaruma's power for that to happen.
The devil warns Nikaido about how her consciousness would not last longer because of the proximity with En. Unless Chidaruma cancels it or En dies or until the next Blue Night, the contract would just be regrown inside her once again, and the partnership will last the accorded four years. They try to understand who staved her in the perfect spot to remove the contract, Asu believes was Kaiman, but Nikaido still thinks it was another person, someone who didn't felt like Kaiman, they find him in a corner, unconscious. En wakes up and using the contract inside him discovers Nikaido's whereabouts, and goes to the church.
Once again we see a series of flashbacks related to Kaiman's past: a young man in a hospital bed, a man saying "Everything goes as planned", people running in fear, a cross-eyes talking at the phone, and Kaiman itself trying to understand what is going on, and the feel that something grim and sick is growing larger and larger inside him. He wakes up, and Dr. Vaux greets him in the Hospital, as he explains some Magic User practice a nasty transformation in his head, the Dr. ask his name, but the lizard head can't remember anything, having amnesia on top of that. A young girl appears and the Dr. introduces her as Nikaido, the girl who found and brought him to the hospital, she wishes him to recover soon, making him smile. Dr. Vaux and Kaiman are arguing about a new name for the lizard head, Nikaido comes to the room and brings some gyozas for him and finds them delicious. As his head resembles a caiman, she proposes that name, he quickly likes the idea, believing it sounds familiar, and maybe his previous name sounded like that.
Kaiman wakes up and is furious at Nikaido for lying to him (and try to murder him too). Showing no mercy, he swallows her head as he did with many other Magic Users to be interrogated by "The man inside his head". Inside it, she recognizes the man as Risu.
Elsewhere in the city of Berith, Risu is tired of looking for the Cross-Eyes and goes to a shop for something to drink. Outside, a masked man recognizes him, and reveals he is a Cross-Eyes too, and both goes to the Cross-Eyes Hideout, a small wrecked house and is welcomed by the rest of the team, with cold tea served in a used plastic cup. The group ask what happened to him, believing he died long ago, and what are his business with them. He angrily tells how he was indeed killed and brought back to life, in hopes to find his murderer, a cross-eyes like them, demanding to meet the boss and even threatening them with his stakes, but is quickly put on check by the same man who brought him there, using his katana aiming at his neck, the cross-eyes hears something and quickly scramble to the outside, Risu asks what's going on, and the leader, explains that is the paper collector, hoping to recycle some newspaper for toilet paper, and also explaining why the whole house is at darkness, nobody uses electricity until the sunsets.
Back in the basement of the Church Kaiman grabs Nikaido and asks what the man said. She answers the same as everyone else "No, it's not you". Kaiman, however, doesn't believe her and Nikaido angrily tells him the identity of the man, as Risu! Kaiman remains obstinate and still doesn't believe anything.