Sorry for the rant but no one can get out of my head that Scar Guy is the antagonist. Here are my reasons why:
Tldr: Scar guy has the means, knowledge and opportunity to, at least fix the friendship, but chose not to
- They banished Est because the guy is weak and could die, but the scar guy is actually stronger than he let others know, and even so, they go through almost all the chapters trying to adapt to the weakness of the girl and the dragongirl.
- Scar Guy has this misunderstanding, angering Est and putting him in even more despair. Instead of fixing the issue immediately, he keeps quiet, and even when Est gets more powerful, he still does nothing to fix the error, not talking of reinstating him in to the party, just fixing the stuff between two childhood friends. Meanwhile, he uses his strength to get the dragon girl to cooperate. Could he not just punch or be punched by Est and then have the two childhood friends talk?
- The author paints Scar Guy as a very knowledgeable adventurer that is able to give advice to both mages and fighters, knowing magic himself, yet he does nothing to help Est, not even advise the girl, who is clearly shocked at almost having Est diyng to just wait or even get them to talk to Est? Instead of this backhanded, totally stupid way of doing things, that, by the way, by the time Est is awakened... is no longer necessary, again not talking about reinstating him in to the party, just mend the bridge and have friends be friends again.
So my theory is that Scar Guy has feelings for the girl and manipulated the party so Est would not grow at the same pace. Also knowing that the second Est is no more, the girl would suffer from the lack of boosts, and he would be there to support her, then alianating her with the eventual grow of Est proving the party wrong and making them have no one but themselves, plus the other two girls, Scar Guy made a harem of excluded girls that only have him to rely on... and the only thing that he had to pay was a random dude and the breaking of a friendship... pretty cheap