I think is about the young dragon having a mother nearby. The monsters were left so the dragon could learn to hunt/fight, the cry is sad because is calling the mother, and soon she will appear.
Maybe the time of summoning is non-linear, so the grandpa and asuka are isekai'ed into the past and fund the ninja clan that Ryoma is employing. That, if Gen isn't granpa himself.
"Kill the criminal who put me in this disgrace. Kill the guy by the name Fulio." I wonder if it can be interpreted as two wishes, so the demon stays a bit after the next wish, and when the guy tries to make the last wish, she's like "NOPE" just to see his face.
By this point, he probably should just drop Eliza. I think that in the fourteen or so chapters since she reunited with Reito, this was the first time she smiled at him. Like she was never happy to see him, just conflicted to see him chasing her.
It also got me thinking about the skills;
Delay Arts: sound like a reactive skill, some kind of Time Compression when attacked.
Arrow of Inertia: that's a Mana absorb
Unequalled Singing: Cecyl used Agility!
Then again, the names don't really fit.