*Smack!*
The boy got launched back toward his group by Iris' punch albeit not so strongly as the other boy who Bill dealt with. Everyone was surprised to see such strength to be released from such a small framed girl, but there was a reason behind Iris' strength.
Even though Iris didn't have any ability which was super good for offense, her natural strength attribute was her strongest attribute, and the reason for that was one that a person without any knowledge of abilities would think is bizarre.
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The reason for this amazing strength was the Healing ability. People who have the Healing ability have to learn how to manipulate and focus their aura and direct it to specific parts of their or others' body parts to repair damage and restore health.