"No, no, that's... it's different. You can fly like a bird, because you are part bird, your lifeforce powers your wings. All living things have mana in them, it is life, and it's constantly burned away just by your heartbeat. Muscles are very efficient, that's why flying with your wings feels so much easier than casting a spell to do the same, but they still burn magic. Even short, temporary spells still burn far more magic, permanently, than your wings do."
Ekrov suddenly squats down, and pinches a piece of dirt between his thumb and middle finger, staring at it intensely as he stands up. He holds out the speck of dirt towards Saeko, then snaps his fingers, the flecks of dirt scattering away--then falling into a floating orbit around his hand. "Even this, a small spell, is burning magic. I only gave it a very, very small fraction of the mana I could have given it, so it will only last a few more seconds, but it's still burning more mana than a muscle does. And either way, that magic is lost now, gone forever." as he speaks, the specks of dirt begin to slow down, individual grains losing their charge and falling back down to the earth. "In the old days, a spell like this could have lasted indefinitely, running off the mana in the air. The tiny loss of mana spent on it would be replenished naturally, as simple as breathing. but now, there is very little mana in this world, it is so little in the air now. Literally, we can test this! You can take the rocks, and the earth, and even the air if you're careful, and melt it down into thaum. It will take great amounts to get even tiny dregs, and that's burning all the matter entirely, turning its basic form into mana!" He pauses and sighs, shaking his head again as the last of the dirt specks fall.
"...Something must have been very different in Japan, if what you're describing is true. To make an environment like that, it must have been the work of a god. One with immense untapped power, and... strange ideas on how to spend it."