Being born in Amegakure, Nomizu's life was never going to be easy. His mother, Hana was his sole parent as his father had left them before the boy was even born. What he knew was that his father was a nobody. A mediocre warrior who tried to be a merchant but got in so fierce debt he never could pay it off - instead of going on the run. Hana assumes he died shortly after leaving them, perhaps hoping that was the case.
Despite this, Hana raised Nomizu as best as she could, but when the boy was 4 years old, Hana got sick. Scarlet fever which Nomizu and a lot of their neighbors started getting. The oldest and weakest among their peers started dying off, and soon the sickness claimed the lives of the younger, too. The children and the retired men and Nomizu was very sick, Hana caring for her son, fearing the worst. But the boy didn't perish. He fought through it. But his mother never did. Hana wouldn't die from the sickness, getting better but being affected by it for the rest of her life. She was lethargic, life-less almost, following the weeks of fever.
A year after the fever, the battles of the greater forces in the world found it's way to Amegakure again. Hanzo's men certainly tried to protect the people, but they couldn't fight off both Konoha and Suna shinobi, leaving the outskirts of the village vulnerable to deserters and bandits. A group of marauders raided the village, murdering and pillaging all they could, Nomizu was but a child, but he had fight in him, arming himself with a kitchen knife he tried to fight the bandits. The bandits mocked the child, bullying him until he finally nicked one of them in the face, hurting him.
Nomizu's home was going to be burned to the ground, while he was left to die pinned to a tree, the kitchen knife piercing his shoulder. But as they had lit the outskirts on fire, a team of shinobi from the Hidden Mist were making their way through on a recon mission and two of them convinced their teammates to interfere, saving as many as they could and killing the bandits, finding Nomizu and a few more survivors. They saved the boy's life.
Hana died in the fire.
Nomizu was raised in an orphanage in the land of waves. When he was 10 and had been at the academy for two years, he got lost in the woods and stumbled upon a hiker - the hiker turned out to be one of the surviving bandits from the attack on his home. The man, Girimono was greatly damage, his left arm was so damaged from the years before he could never use it again, he was blind in one eye and his ear was torn off, but he recognized the boy - he had been there when his chief stabbed the child with the white and blue-hair in the chest and pinning him against a tree.
The last few years had made the man resentful of his old self and he asked Nomizu for forgiveness, offering the boy a meal by the campfire, which he accepted, hearing him out. They talked the night away and in the end, Nomizu understood that there were circumstances that had made Girimono do what he did, he wasn't evil. He forgave the bandit, and upon hearing this, Girimono cracked a smile and handed Nomizu a treasure he had kept for many years, a blade he had stolen from a Samurai who had died on the battlefield - a very odd blade, perhaps influenced by the Seven Swords of the mist. Girimono himself was no swordsmith, but he knew the blade was just high quality and if Nomizu wouldn't use it - it'd at least sell for a lot of money.
The blade was called Icebreaker and it had been his most treasured possession ever since, and it solidified the belief that he needed to be better. His actions will affect his destiny, and this would drive him forward in the years to come, into the academy and into the beginning of his time as a genin.