Yeah it has an prequel chapter called "Yugami hajime"
No, I know what you mean, I remember seeing an extra or something where the sensei has the kid on his lap(eekers) and he's like telling the kid to be good or something, but idk where that went
pretend im not replying to this months later but is it this youre talking about? https://www.mangago.zone/read-manga/yajirushi/ (chapt 1.1 near the end)
I checked chapt 1.1 rn, but no, it's not that one. It was like it's own little chapter, and I've never seen it again. 'Tis a mystery ╮(￣▽￣)╭
I swear this used to have an extra chapter