Unmeig could not hold himself back.
For him, anyone who opposes him is his enemy and anyone who stands by him is his ally.
Why did he fight Renir back then? It was because Renir stopped Ernanfo from helping Unmeig.
If someone is an obstruction, then that someone is an enemy!
That was the simple rule within Unmeig's head. Renir didn't explain himself for them to battle.
Only after when Renir got his results did Unmeig knew his intentions. As a result, the Spirit Runer admired Renir, going so far just to get stronger and to receive such heavy burdens for himself.
However, that was far from enough for Unmeig to trust him.
A messenger from heaven came down, giving mercy to the world. Even if Unmeig was prideful, his top priority was for the safety of the world.
But to the world's shock, Renir actually made an enemy of the entire Celestials. Unmeig didn't understand how it happened but he understood the Angel's last words.