Shoma Yusa is the protagonist of the Yu-Gi-Oh! OCG Structures manga series.
He is a soft-spoken and shy boy who only recently moved to the big city at the invitation of his older sister Ageha, but is more than ready to throw himself into the card game he loves.
Just like every other protagonist, his name also contains "Yu" in it, expect it's placed within his surname similar to Jaden Yuki.
Shoma initially used to live deep in the countryside where he would have to wait at least a week to get the latest OCG packs. The only person he could duel with was his older sister until three years prior when she moved to Tokyo for a job. During that time, Shoma collected a lot of decks but could only play against himself.
Recently, just as Shoma was about to start middle school, his sister announced to him that she would be moving close to the Satellite Shop (a Yu-Gi-Oh! speciality store) and offered Shoma to come live with her in Tokyo which he agreed.
Ageha is Shoma's older sister who played Duel Monsters with him for most of his early childhood until she moved away. When she moved closer to a store centre around the aforementioned card game, she offered Shoma to live with her so he could play with others instead of all by himself.
Jukyu was the first person Shoma duelled in three years when they met at the Satellite Shop. After their duel the two insistently became close friends who often play against each other for fun.