Sanyu grew up in a very tiny town, population of a mere 70 including his own family of four. His parents were farmers, and though Sanyu aspired to be more there was no real out for the residents of this town. Originally born Himawari Sanyu he was expected to work on the farm until his parents passed, find a nice girl and continue the family business, unfortunately experimentation with a member of the same sex spread throughout their small town and he became a social outcast. Since he no longer had friends and would often find himself the aim of bullies he stayed out of sight. When not working on his family's farm he would spend time in the nearby field of flowers, mostly consisting of pale white to yellow. This allowed Sanyu to blend in with his blonde hair.
During his time as an outcast a man by the name of Umashi would occasionally visit, as the village was between others and had occasional visitors stop by the inn to rest. Within a year of this man coming Sanyu began to experience supernatural phenomenons, crops that he was working on would grow quicker, strangely enough some even within the next day would be ready to sell. Nobody quite understood this, but the family was able to link it Sanyu's crops. They used Sanyu's crops to feed the family while the rest were sold in town normally.
The man named Umashi, however, recognized Sanyu's abilities, attributing it both to natural energy manipulation and a bloodline that he himself also shares, one to control plants, or the element of "wood" as he called it. Umashi offered to take the boy with him, but his family was vehemently against this idea, as Sanyu was key to their continued survival and success, and they didn't want the man filling Sanyu's head with any form of hope so they made it forbidden for them to meet, threatening to get Umashi banned from their town. Though Sanyu would attempt to meet the man on several occasions anyway, learning more about chakra and how to manipulate it.
Sanyu, wanting to help his family, used his new knowledge to increase the productivity of their crops. This allowed them to have plenty to eat, plenty to sell within the town, and the ability to sell to nearby towns, increasing their profits by quite a bit. Unfortunately this made many within the town jealous and would often attempt to spy on them to see their secret. This is how they caught Sanyu using his chakra to grow crops, but they viewed this as witchcraft. He was only 14 when the town, with their lit torches, took to their fields and their home and set it all ablaze. In their attempt to escape Sanyu got separated from his family, unable to return to them, he went back to the field of yellow flowers, hiding in plain sight.
He never attempted to go back, unsure of the fate of his family, but he was now alone. He stayed in the forest, away from the town and survived by manipulating nature to feed him. It was then that he was found by Umashi and a woman, who introduced herself as Yomi, and their kids. They planned to retire in cloud, Umashi recognizing Sanyu and hearing his story invited Sanyu to finally go with them. Incapable of of finding his family he dropped the name Himawari and joined a new family, the Yamamoto clan.
Once they got to the Cloud village Sanyu continued his training, while also beginning training in all forms of being a shinobi. He spent very little time in the academy, he was already 14 years of age and had some training in ninjutsu that he only needed to learn the other basics. He grew fond of genjutsu, even more than his affinity to wood ninjutsu, and even learned the art of kenjutsu. Once he became a gennin he spent most of his time helping others in most of his basic missions, though he later realized he gained a real thrill in battle. Not wanting to just fight other shinobi mindlessly he took to monster hunting, He joined others in groups to fight, and actively worked to make sure others were protected. He felt obligated to make sure everyone was safe, since he couldn't do the same for his family. His actions protecting others is what got him promoted to chuunin rank.
Unsure of his future in the shinobi world he began going to regular school to learn other trade skills, if something were to keep him from protecting people he could become some sort of herbalist, or even a gardener. Though he didn't want to be a farmer when he was with his family it was almost as if being a farmer was his only connection to them.