From the spoiler that i read it's bcause his heart is absorbing dark power. And holy sword can only be held by someone with pure heart. Or soemtjing like that.
You can find it on spoiler in the comment tho
I think I heard someone say he had dark magic in his blood and was barely able to hold it before but when he touched the pillar the dark magic got stronger and obviously the holy sword dont play with that
I think there was a spoiler that he ate(?) The demon king's heart or sth to turn back time after Yvona died in the past. Basically Yvona returned back to the past cuz of him and the dark power awoke in him when he saved Yvona in the .......(i forgot what it was, sorry(• ▽ •;)) Anyway he can't use it cuz of that
Does anyone know why the holy sword keeps rejecting him? Spoilers are welcome lol