"Here is the sacred beast that you died for, and who resurrected you.
- ..."
Make him express disbelief, or awe, or maybe anger at the farce this child is pulling... something!!! There can be a large number of possible reactions, and the manga went with "meh"?
Just kind of a somber expression at first, then full acceptance as if that was everyday occurrence to them. That is so underwhelming.