Whenever Japanese people go on vacation, they buy presents - snacks, usually - for other people. Part of it is the desire to share food or local treats that aren't widely available with those who couldn't make the trip. Part of the custom is expressing gratitude. And then there's the fact that, well, it's sort of expected!
Website Gigazine recently visited the Neon Genesis Evangelion exhibit at Fuji-Q HighLand at the base of Mount Fuji. The site sampled all the available Neon Genesis Evangelion snacks in most obsessive detail.