So basically magic is stored in the dick and instead of exhausting the excess by working out or something he just fucks off that magic or else he dies?
I read some of the novel a long while ago and the manga does a bad job explaining it.
I think his excess magic is what causes his libido. And in times of peace it has no where to go so it builds. Then the libido fucks up his concentration and he'll explode if he doesn't err...explode in other ways.
I think
It's been a while. ╮( ̄▽ ̄)╭
Boi literally said ♂