Rin’s parents met in Mahoutokoro, marrying about a week after graduating. Due to his father’s...difficult rich family, the marriage was extremely strained. Despite not being the oldest nor the heir, the Sasaki’s detested Shiro’s (Rin’s father) wife, Siu, for being a muggle born korean. The old family still held some prejudice dating back to the invasion of Manchuria, and of course valued blood purity. After two years, Shiro and Siu grew so fed up that Siu took a job offer at Ilvermorny to be a Transfiguration teacher, and moved. By that time, little Rin was barely one, and hardly got a chance to know his home country of Japan.
His early years were average, perhaps a little too average for his liking. They lived off his mother’s salary as Shiro tried, and failed, at being a self help author. They made enough money for them to have what they needed, and little else than that. His parents didn’t really pay mind to him, however; his mom was always away at school, and his dad was focused on his writings. Thus as a youngin, Rin never got the attention he really craved. Lucky for Rin however, they did take the time to teach him Japanese and Korean.
When he was about seven, one event changed his life. Shiro brought a toy broom for Rin to play with and be distracted. At first, he was disinterested; all it did was float afterall. Seeing the broom wasn’t working as he hoped, Shiro put his son’s favorite stuffed bunny on a high shelf and told the boy to get it. Rin hadn’t had his first sign of magic yet, so all he knew he had was the broom. Rin attempted to ride it around to get to the top shelf, but the broom wouldn’t go above two feet. After wishing and wishing, some of his magic kicked in to influence the broom to float up, giving him the power to grab the stuffed bunny. His father was in shock. He figured he bought a different model broom, but when he asked Rin to do that again, the broom wouldn’t fly up, proving it the boys first stunt of magic. Seeing this as a sign, the unsporty father introduced Rin to quidditch. He wouldn’t know this would become the boy’s second love.
When time came, Rin went to Ilvermorny, being sorted as a Thunderbird. It was there he realized he would never be a genius magician, but had a potential future in quidditch. It was also there he discovered how fantastic flattery was. His parents had never taken the time to recognize his worth and achievements, bar his father’s move to introducing quidditch. He was a natural, and grew cocky about it. Nothing made him feel better than school kids cheering his name. He became unruly, disobedient, rebellious, and all other teenage aspects at preteen age. His mother was embarrassed her son could make her look so bad because she couldn’t control him. After a discussion with Shiro, they decided to send him to live with his grandparents in Japan, to learn discipline. Siu may not like her in-laws, but she couldn’t deny they could teach that. Shiro also figured it would be a chance to rebuild a bridge.
Thus he moved to his grandparents at 13, and transferred to Mahoutokoro. It was extremely difficult at the beginning because, although he did speak Japanese, his writing skills were absolute crap. They did have a really good quidditch team however, which he joined. There, he /somehow/ made friends with Kiyomi and Haru, who helped him with his writing skills so as not to get kicked off the team. Most could recognize his talent, but had a hard time breaking his laziness and cockiness. Rin never managed to lose the latter, but he did become much more hard working from there. If he wanted to stay on the team full of powerful players, he had to.
Rin chose to stay in Japan, and graduate from Mahoutokoro. He became a seeker/keeper on one of the Japanese quidditch leagues. When he was 19, Japan decided to place him on their quidditch team, hoping he could lead them to the quidditch world cup.