If the author changed the main character I'm really going to cry my ass off😭

No that won't happen. As it stands Ryoma has beaten most of his contemporaries so now they need a new challenger especially now that he's playing for America and the Japanese team is out to prove that he made the wrong choice. Someone like Kintarou who's small like Ryoma and supposedly has more raw talent presents a great opportunity for Ryoma to grow even more.