About the possible time paradox, Trayner explain to Eirth about the impossibility of that, because if you changed something in the pass is not a real change just a change of perspective of what really happened, just like if you get back in time and kill your grandfather you are not gonna disappears that just means he was not your real grandfather (the poor bastard was just a cuck), the so called Grandfather Paradox, something like you cannot change past events just the "perception" of them, so not weird time lines shit in this manga/novel just stay in the classic..