Unlike the characters' regular human forms, their Kaiju forms are several stories tall and capable of dealing a lot of damage to city property and eating the public who are bite-size to them. If they suffer too much damage they may shrink back to their normal human forms and be at risk of being prey to the other Kaiju. If they touch toxic waste in their normal form they can turn into their Kaiju form and if they eat people in their Kaiju form it will restore health and stop them from turning back into their normal form. Eating toxic waste when in Kaiju form will give you super powers. Aygear can cause storms that knock people back and blow things away, Addan can wrap up things in his coils and mind-control people to stun them temporarily and Jarmo has a frenzied attack that rapidly does damage. Whilst smashing the city you are graded by how much damage you do and the winner in these competitions is the highest scorer. Try to prevent the boys from getting the highest score and winning instead of you.
Addan is a girl pretending to be a boy in this canon. Males make for good villains as they often think of themselves first, which means in this case that the boys are likely to do bad things and more likely to argue among each other. Trying not to make enemies with this potential threat will make you enemies with your friends and fighting the boys puts you at risk of being food for them. Also often the boys' selfish motives will mean they are a constant annoyance to your happy friendly group.