Denji is the protagonist of the Chainsaw Man manga series. He is a naive teenage boy with blond and ratty hair with razor-sharp teeth. As a young boy, he inherited a lot of debt from his father on his shoulders. After his father dies the old Yakuza man makes him pay the debts.
To do so, Denji works harsh jobs to earn money. One day he takes up a job of eradicating the tomato devil after which he gets paid but unfortunately all the money goes to the yakuza. The taxi driver gives him some money after he completes the dare of eating his cigar bud (which he of course spits out after the driver leaves). With that money, he can buy bread. As he eats the dream thinking how “normal” people eat bread with jam when Kid Denji meets injured Pochita, the original chainsaw devil.
To heal him he gives Pochita his blood and forms a close friendly bond between a devil and a human. He convinces the old man, yakuza, that Pochita can help eradicate the devil to which he agrees and Denji becomes a devil hunter. This allowed the debt that filled young Denji to be dealt with by becoming a young devil hunter with the help of Pochita.
Later after being a Demon Hunter his whole life Denji was betrayed by the debt collector and brutally murdered by zombified humans. Inside the dumpster, where they were fighting the zombies, some of Denji’s blood gets into Pochita making him recall a memory of Denji mentioning that he heard some devil can take over dead bodies and that if he dies, Pochita can take his body and fulfil his dreams.
How Did Denji Become a Chainsaw Man Devil?
Pochita, to save his only friend, heals Denji, sacrifices himself and becomes Denji’s heart. By doing this, Denji becomes a human and devil hybrid. He can utilize Pochita’s powers by pulling on the cord on his chest he gets after Pochita becomes his heart.
The powers Denji acquired after making a pact with Pochita made it possible for him to transform into the Chainsaw Devil. The power had one drawback which was if Denji lacks blood, then he would not be able to transform properly and will be much weaker. By turning into a hybrid devil, Denji also gained a lot of inhuman life force, strength and abilities. With this, they (Both Denji and Pochita) live a “normal” life.
After a lot of turbulence in their normal life, in the recent chapters, we come across the reason why Pochita helped Denji survive. Pochita had only one wish, to be hugged by someone. His wish was hard to fulfil because people were afraid of his powers and strength. Due to this, his wish seemed like a lost star which was found by Denji. To thank Denji, Pochita gave him his power. Denji and Pochita, fulfil each other’s warm and sweet dreams and come to a powerful bond of fate giving Denji his powers.