"Once, I was tasked to lead the Demon Race in a Shadow World, helping them to overcome a crisis. Through my interaction with the demons, I indeed learnt about their culture and characteristics deeply."
As a Principal, it's always his duty to guide students no matter when.
That has been Lanci's professional attitude all along.
If Duchess Cloris were negotiating with him and exchanging information as a noble from the imperial capital, he might not say much.
But she had chosen to ask for advice as a student.
Then Lanci would simply tell her the answer.
"Oh, really?"
A reason that sounds offhand but is surprisingly logical.
The only question left, how did this absurd Shadow World appear under an even more absurd historic backdrop?
Unfortunately, like a question in front of them, Lanci could only write down the answer for them, but couldn't make his subjective inference as evidence to convince everyone.