Byung was safe but there was never any threat of Jae-Bong being injured throughout their brief fight because of his strength and overwhelming experience that he basically one shotted a kid that might be the key to sorting out who was behind this attack on South Korea.
This was too shabby to be orchestrated by an analytical genius, and this meant it was done by a bunch of amateurs because there was no other way that a 15 year old as weak as this was given the task to attack a Guild Master or someone as important as Byung.
Ae-Cha carted the child to the guild HQ with Jae-Bong taking a detour with Byung because he knew that this was not something Byung should see.
They needed to preserve what goodness was left in him and that included reducing the level of cruelty he was exposed to by events around them.
"Where are we going?" Byung asked Jae-Bong