@comradeprozac
The thing is, before your post, this was just a crossover. Nothing more than a non-canonical chapter that informs people of the upcoming anime and invites a guest character, who also happens to be a Japanese stuck in a fantasy Isekai.
There is nothing in this chapter that would even hint at anything being a spoiler to anything.
Until your comment, that is.
You've just posted a spoiler by accusing a seemingly innocent chapter of being one. Well done.
Sometimes, a spoiler isn't a spoiler, until people realize it is. We call that "foreshadowing".