You can get a lot done in twelve episodes if you pick one thing and focus on it, whether that's a character or a theme. In 'Chainsaw Man', a lot of things happen, often violently, but not in great detail or depth. It wanted to deliver a series of shocking moments, and the plot had to be stretched pretty thin to cover them all. I guess you can patch it up with flashbacks, but the end result lacks the polish and precision of, say, 'Akiba Maid War'.
Typically, to deliver a shocking moment, you put a normal person in an extreme situation. There are essentially no normal people in 'Chainsaw Man': innocent bystanders barely exist; ordinary emotions barely register. It can be intense, but without that normal baseline, it's difficult to know how to feel about strange anti-heroes fighting equally strange villains. It's certainly dark: darkness takes centre stage, in Hot Topic eyeliner. Characters obsess over death and revenge; get drunk or go insane; kill brutally and die horribly. Again, it can be intense — more so if we knew them better, but that takes time and restraint. You can't ask me to care about someone you've already blown up, no matter how big the explosion.
Flashbacks are not actually a substitute for proper pacing and structure. If you want to introduce a major threat, consider foreshadowing it. Change the source material if you have to: there's no law against it. Imagine if, say, the work relationship between Aki and Himeno developed in parallel with Denji's origin story; it might highlight the difference in the characters' motivations. The first eight episodes could have been stretched to a full twelve, with a little extra world-building along the way: it was really at its best in the mid-season as a monster-of-the-week workplace action romantic comedy. As it is, Himeno, a fine character, is given too little attention; with enough flashbacks, we do learn quite a bit about Aki; Power's comedy is always welcome, and Kobeni's too. Unfortunately, the protagonist is Denji, a shiftless idiot defined by his lack of both depth and agency. Denji works fine as a joke; as the show's main character, he fails to drive the story forward.
All art is dedicated to joy, said Schiller, who invented dark, and I wish there were more joy in 'Chainsaw Man'. Is a beach episode too much to ask for? What I mean is, I've seen joyless, nihilistic subversions of the superhero genre, and other genres, many times. I know you can kill people with a chainsaw. Maybe next season we'll find out why that matters.
