After he began using Armor Slice, Toz's sword cut through the buffalos' demonic energy, and when he improved it using his mana vision, he cut through their bodies as well.
His sword shone as he swung it through the air. Blood sprayed as he chopped off legs left and right and slashed open buffalos.
The bloody and fierce battle made Toz's own blood boil, and he excitedly hacked away at the buffalos.
However, he quickly realized that he was too excited. Using Armor Slice made it easy for him to defend and counterattack the buffalos' attacks. Too easy, in fact.
If he wanted to kill all the buffalos as quickly and smoothly as possible, Toz would have used his magic from the start. But he didn't because he wanted to train his swordsmanship skills. After realizing that he was wasting valuable sparring partners, Toz stopped using Armor Slice and went back to only reinforcing his sword to increase its durability.