Reference for the voice can be heard here!

Leon is a passionate, hot-blooded young teenager. He often slacked off from studying and baseball practice; however, his baseball skills were never diminished due to his status as Ultimate Baseball Star. In fact, he hated to practice, seeing no point or enjoyment in it because he was already so talented. Due to his natural physical talent, he considered even very difficult and unusual feats easy and had some trouble empathizing with people who lacked such talent, as he didn't fully realize how hard the bet he made with Kanon really was.