@CommieJohnTeh @animekek69 It has been established that some portion of the heroes were isekai'd into Goblin-san's world.
Of course, one could argue that it's only isekai if it's a focus of the narrative but, then, you have plenty of stories tagged as isekai that only note the isekai aspect in the prologue and then never reference or hint at that fact ever again. So.. by current considerations of the tag, this should probably count as an isekai. From a utility standpoint, however, neither this nor the tossaway isekai mention stories should count, since the function of tags should be to tell would-be readers key aspects of narrative. So there's a lot of room to just interpret this story's isekai status by one's own preference.