Complex sentence: The story follows a piano prodigy Kōsei Arima, who had become famous as a child musician after dominating many competitions, however, after his mother died, he could no longer play the piano.
Split into simpler sentences: The story follows a piano prodigy named Kōsei Arima, who had become famous as a child musician after dominating many competitions. However, after his mother died, he could no longer play the piano.