Ahaha I love that misunderstanding at the end. He is asking a way to USE more mana, Root thinks he is asking to GAIN more mana. That’s a good way to have that be explained in another chapter, giving exposition without it feeling clunky. I like it.
No, in RAW he's just asking "even more magic power? you seriously saying that?" Root got the message just fine, it's just that what Makoto can use is at absurd level already (remember he created a lake before?) that Root is shocked he want to push even further.
It's weird how Tomoe just explained how Makoto gets angry about curses and stuff regardless of if it happens to him but then the twins see his face and get the feeling that he doesn't care about anybody else.
The TL over-simplify the line and lost the nuance of it.
The exact line, more literally translated is "He shows absolutely no interest in the opponent before his eyes, that sort of feeling..."
Which refers to assassin-mode Keema/Morris and sort of refers back to when Tomoe recruited Keema, that she (and Morris) had the mindset to be able to even eat next to their victims' family.
So it's not that he doesn't care about anyone else, but more that if he view something as 'enemy' then nothing about them matter he'll only think about how to delete them.
Noble, commoner, rich, poor, hero, villain, etc. doesn't matter, once he get into that mindset you're fucked.
(obviously before he switch into that state he might care about those things)