As a quick and mostly spoiler free rundown, The Brotherhood of the Tofu (Yugo, Amalia, Groovy, Eva, Ruel, roughly in this order) become more and more shit bags as the series goes on. They buy into the "we're the heroes of this world" thing way too much and start getting incredibly reckless and doing more and more risky things, as well as think about problems less as they can start solving them with just their strength and skill.
Yugo and Amalia are the biggest offenders though. Yugo nearly destroyed the world because he wanted to play hero and to get his dick wet with Amalia. In doing so he gave birth to a race that was destined to slowly die off and suffer and couldn't care less.
Amalia was even worse, she was going to marry the King of another kingdom, the King planned the marriage for three goals. He legit did love Amalia, wanted to save and secure his Kingdom and also hers in the process and possibly other kingdoms as well if things went well. Finally to combine their two nations together to be stronger and better for both of their people. His kingdom was cursed to forever be a horrible frozen wasteland that everyone would die in, so he built a massive bunker complex that was heated by a powerful artifact and by burning trees as firewood. However once Amalia found out that the Count planned on using wood as firewood she flew into a pure autistic fit, told the Count to go fuck himself as they were just about to seal their vows, attacked him and ordered Yugo to steal their power source and shut down the furnace, damning the entire kingdom of people to freeze to death at best, starve to death in the cold at worst.
Yugo then used this power source in a way that almost ripped the world a part because he felt like playing hero.
Over all they turned into shitty people and Adamai and Oropo (the guy who "cucks" Yugo) were 100% correct about everything.