The Guardians of the Tree God are the descendants of Hagoromo's children and their transmigrations, children who thought more like Ootsutsukis than humans.
These children protect (rather watch over) the Tree God of their own choice, since they knew that Kaguya's disappearance would attract the attention of the main branch of the Ootsutsuki Clan (those who are aliens), and that these are parasites that only pass from planet to planet collecting the Fruit of Chakra without caring about the lives of the local beings.
These children also consider themselves parasites, and believe that both Hagoromo and Hamura are fools for not having eliminated in a more permanent way (such as death) the threat known as Ootsutsuki Kaguya.
"I know she's your mother, and that you love her in a way, but leaving her alive is the same as leaving a time bomb for future generations. You may be almighty, but one day, you're going to die and she won't, and when she wakes up, because yes, she will, there will be no one to stop her. And don't ask me to stop her, because I want to see the expression on your face when you know that I was right. "
These children take no one's orders, and will do what they think is right or fair at any cost, even if they have to kill their own parents or annihilate an entire village.
Unlike their parents, these children are born with their memories of their previous lives, so dying is just a body transfusion for them.
In each reincarnation, whenever the sun and the moon pass away, that is the signal they use to seal their current bodies to the Tree God, and begin their journey to the next life. Because of this, and for another reason, they have a vow of celibacy in order not to leave any offspring.
The other reason for this vow is that, not for looking arrogant or anything, but these kids have an impressive chakra reserve, in addition to possessing the ability to get a Rinnegan, and they know that one of the reasons Kaguya turned an evil and power-hungry being was because she wanted to "regain" the chakra that her children had "taken" from her.
"And they tell us that we are exaggerating. If a mother, who is supposed to love her children, wants to kill her children for something they inherited from her and that she claims was taken from her, it is clear that this woman is a danger and must be stopped due to the safety of others "
"The reality is harsh, so it is time for you to accept it. Peace is impossible, because despite the fact that somehow we managed to make peace reign on this planet, someday some uncle or grandfather of ours will come down from space. and he will not hesitate to annihilate us all for power. "
These children are warriors. Its natural habitat is a battlefield, not a hidden village where peace reigns.
"Do you want to survive? You better mentalize yourself to kill or be killed."