He doesn't know why, but, probably because of his instincts since the last time he already saw you injured but the injury can't get healed by magic. It has to be natural regeneration from your body in which takes much longer.

That's why every time a problem came and you were with him, he always prioritized to keep you safe from any danger even though he can easily defeat them without trying much.

One day when he is done with the enemies, he just remembered about you and within a second came to your place, unfortunately he was too late. Your body was laying on the floor, with poodle of blood throughout your body and the ground. The injury you took is definitely going to make you die.

He, who is the strongest yet cannot save a person he loved.