[While all this time he considered this power to be rather useful, now he realizes it may be a curse, too. With great power come great responsibility...

A responsibility he didn't want.]

It's just...ugh, you do know how mana exchange works, right? [Because right now he wishes he didn't so he wouldn't have to explain this.] Physical contact speeds up the intake from the atmosphere and apparently that's the key to opening the door. It's all about the mana flow, the door seems to react to it...

[Somehow he can tell it's not the best explanation, but surely the best one he can provide now.]

Who's going to do it?

[Here, someone had to say it.]