I’m no fan, but I know the basics:
So basically the story is set in a world infested with monsters referred to as Demons. The main character, this kid named Denji, hunts these down for money while he tries to find the truth about his father’s death. He ends up befriending a friendly Demon named Pochita, who has a chainsaw nose. But then Denji is attacked and was about to die when Pochita gave him a chance to keep living - by letting Pochita replace Denji’s heart, fusing them together. After that, Denji notices a strange string attached to his chest where his heart is and pulls it - and discovers that, by fusing with Pochita, he has turned to a half-Demon, with chainsaws sprouting out of his head and arms. And thus Chainsaw Man is born. Soon, he gets scouted by Makima, a strange woman who runs a Demon hunting agency and gives him the choice to either die or work for her hunting Demons. Being desperate for money and a place to stay, Denji picks the latter.
That’s all I know. Now, any questions?