An update! It's been so long!
Sorry for leaving this series stagnant for 5 months. I got too busy with academics and encountered some problems irl, which kinda fucked up my entire workflow, but rest assured, I'm planning to catch up on this series as fast as possible. 🙇♂️🙇♂️🙇♂️
Awesome!
There's no way he's doing anything on this trip, but I can't imagine what he's planning. Is he hoping to cause some sort of barrier interference, or perhaps create an opening for someone else to infiltrate?
Since only members of the ducal house who have inherited their special eyes can enter, I'd say that they might have been led to meet someone else from a ducal house, like the head of Remington, but well, the room is well guarded and only has that entrance, so it's not like they could be smuggled elsewhere. So seeing that the room is empty is not too surprising.
I doubt he knows anything about barrier interference and it's not like the barriers block people; the only thing members of the ducal house go in that room for is to replenish the mana stones to ensure the barrier keeps running.
I don't think he'll do anything crazy like invite them to touch the stones because they're little children and they shouldn't even be learning to control their mana at that age.
So that leaves two things, he either tells them about the history of this room, that binds the royalty and ducal houses of this kingdom, or he demonstrates himself how replenishing the stone's mana goes (and likely how tired he gets afterwards), mostly as a means of teaching them the responsibility (or their chains) that they have towards the country. It's a pretty important lesson though I'm not really sure they need to be taught that already at their age. I mean, Marcus himself says that as a child he was just cluelessly running about in the garden.
Also, Marcus claims he has received permission for this from the prince, so whatever he's planning must have been approved (and if he hasn't received permission, he's going to be in trouble, you can't just claim to have the prince's approval like that).
Anyway, we'll just see next chapter.