After the conclusion of the battle between Chainsaw Man and Makima, we are led to believe that Makima had succeeded in her objective since we see her ripping pochita out of Denji’s heart. However, in a surprising twist, it turned out that Denji had used the blood given by Power to hide among Makima’s guards while keeping both bodies alive to deal Makima a crippling blow when she let her guard down.
It is clear that this would not be enough to kill her since she has survived even more precarious situations. Even if he does kill her, she would just be reincarnated in Hell and eventually come back to the mortal world. Although she wouldn’t have retained her memories, it is still a very uncertain and anxious position for him given all the pain and heartbreak she has inflicted upon him.
Then Why Did Denji Decide to Eat Makima?
This is when he comes up with the most “Denji-like” plan you could think of, and decided to chop up, cook, and eat her body. Being Chainsaw Man, this would mean that her existence would be erased leaving her dead for good with no way of returning.
With this conclusion, we could say that Denji had found his own sick and twisted way of achieving his goals since all he ever hoped to satisfy in life was his hunger and lust, and by eating Makima, he “becomes one” with her while fulfilling the desires of his stomach.
This is quite the vile analogy that you could only expect from Chainsaw Man. As for Makima, she had stated earlier that she wouldn’t mind being eaten by Chainsaw Man if her plans failed to succeed, but we also know that she only looked up to the original Chainsaw Man and did not care for Denji.
Hence, we can only imagine the disgust and disappointment she would have had to be taken out in this way.