The mangaka of Dandadan was the assistant for the mangaka of Chainsaw Man. That should tell you everything.
Also don't take that the wrong way, Dandadan is it's own thing and at this point I like it more than Chainsaw Man.
If you want a teaser, without giving out much away, the story is about
That to me is the side story. Idk, it's probable that my expectations are wrong at this point. I'm pretty sure they are, but for me the story devolved and started being cookie cutter. The jokes were funny up to a point, but they cannot carry it for me. The mangas name is Spy x Family after all, so I don't know what I'm expecting at this point.
You won't be disappointed.