As a marketing analytics & research person, I think the biggest issue here is that the WHY of choosing to reach out to cosplay YouTubers isn't clear. Why would people watching cosplay videos like to order candy from Japan? As opposed to say people who show food recipes from other cultures etc. In this kind of marketing (basically word of mouth on steroids), the context and content I have observed from watching brands really take off are much much more important than the mechanics.
I think the reasoning could be that most people who like cosplay have at least some interest in Japan.. which sounds like something I would expect to be true.
Yes. However the business objective isn't finding people with interest in Japan. The objective is to reach people who would likely be interested in buying exotic candy. The further removed from your objective the marketing vehicle is, the exponentially higher the likelihood that the marketing campaign will fail. While I suppose Bemmu hasn't really been a marketer before, I see even "professionals" making errors like this all the times in search of chimera like "engagement" rather than linking marketing strategy and execution directly to the business objective.
buying exotic candy...from Japan. Having known a few people who are into manga, not even cosplay, they often find oddball Japanese candy interesting. Maybe not enough to buy because of an unboxing video, though.