I honestly love how the author didn't make the knight girl love the MC and turn this into another harem manga, but instead ship her with another side chara.
Now Zagan's off hand comment about mana transfer is a smoking chekhov's gun. I'm gonna bet Barbatos will need some sort of mana infusion to recover and Chastille's gonna provide it.
who could it be... someone that didn't get affected by a flash, probably someone blind 😆😆, author is really bad at trying to use mistery for the characters (like the girl possesed by the shitty shota).
btw I love the series it has other good strenghts.