Two years (1)
With his core being different and his meridians reversed, he found he could practice more than one [Mana Accumulation Technique] simultaneously without damaging his core.
It was like forming another core in his body, which did not make any sense at the start, but then, as he closely inspected his body and experimented with it, he realized that thanks to his unique condition, the mana was flowing in the reverse direction, the cores would not get entangled.
This realization opened new possibilities for his growth and power.
But at the same time, it was hard for him. No matter the mana accumulation technique he saw or learned, he needed to adapt all of them to himself.
At the same time, the other cores were not completely unlinked to each other. Their energies needed to be balanced.