Gotta say i'm loving the peptalk about "What's makes the demon lord? Power, authority, title, position? Nah, it's me.".
Not just because of how badass it is, but also, when you remember how supposedly the purpose of the school and the gathering of the Demons students who has chance as the reincarnation vessel IS to welcome back the Founder, this selfish yet hilarious remark suddenly have an intriguing depth.
The school works in such a way that they are basically giving anyone a chance to be the one and only Founder, as long as they managed to become the top of the school. Why do such roundabout way like that instead of directly searching among students who has the most abundant or whose root is most similar to the Founder's root? That's definitely a red flag.