@moozooh You might be correct about not wanting to ruin a fish, but nothing in the chapter looks like smoking. I don't need to read Wikipedia to know something I've done, myself, multiple times in my life. That being said, I'm not sure how much heat twigs and cones are going to produce, so it's possible he won't be burning his dish. If he had good wood burning, he would obviously need to take the fish further away, like you'd make flamed salmon. He's just burning some trash, though. They might be severely lacking in joules. It's not like I wouldn't have ever burned twigs and even cones. They are good for getting a fire started, but if you try to heat up your sauna using only them, you'll be disappointed.
I have a feeling the whole thing is a joke in the sense that usually you see the setting in the chapter done with proper charcoal. Satou just is so wacky he won't go buy something like that, instead he fetched random stuff from the backyard or a nearby park.
Edit: Actually, I'll have to admit one thing: I keep forgetting the Japanese love eating raw fish, so for all I know, Satou could indeed just want to have a bit of smoke flavour on the skin and otherwise perfectly happily eat the fish raw (and wriggling).