Dramatic Entrance
When Leon arrived on the edge of the battlefield, the battle was so intense that he was not noticed at first. He saw his three summons putting up an intense fight against a single man. From them, he could tell that he was incredibly strong. However, he was yet to personally step in. He wanted to observe the situation first before making his entrance.
He was not the only one that was watching the situation. Several powerhouses on both sides that had chosen to stay back and wait for an opportunity were also surveying the field to see when it would be best to intervene.
The most likely battle to intervene with was the ones where Low A ranks fought against each other. That was the thing when it came to battles. The tiniest slipups were enough to result in a fatality. This factor was even more exacerbated when it came to battles between A ranks.