Kimetsu posts good numbers in the west and is very big in asia, season 1 is one of the most watched series on bilibili (china) afaik and the manga was among the most read, was regularly #1 by a big margin on manamoa (korea) as well. Worldwide would probably be big but not big enough to surpass naruto or DB in overall sales, this seems like kind of a weird argument to have though lol, KnY only has 22 (soon to be 23) volumes worth of content after all. I would say the final number for 23 will probably be like 120mln or so, higher if they decide to include ww into it, it'll grow through new editions etc. over the years but 250mln is setting the goal way too high imho, I doubt it'll get even close to be honest. That would mean an average of almost 11mln copies per volume (or a bit less due to novels being counted in), it's not even halfway there, so i really wonder why we're even having this argument when it should be a pretty clear no.