Shohei Ohtani began playing baseball in the second grade of elementary school, and from a very early age, he openly said that he wanted to become a baseball player.
According to Hideki Kuriyama, who was Ohtani’s manager during his time with the Hokkaido Nippon-Ham Fighters, becoming a professional baseball player is not something that can be achieved with a vague dream like “It would be nice to become a baseball player someday.” One must decide firmly — “I will become a baseball player.” Without that level of determination, it is extremely difficult.
Ohtani seemed to believe from an early age that he would not just want to become one, but that he would become one.
So why did he want to be a professional baseball player in the first place?
When adults around him asked, “Why do you want to become a professional baseball player?” Ohtani’s answer was simple:
“Because I love baseball.”
Many children answer questions like this by saying they admire a particular player or support a favorite professional team. However, Ohtani as a child rarely watched professional baseball games in person, and he hardly ever watched baseball on television. He did not have a specific player he admired, nor a favorite team he rooted for.
Even so, he loved baseball purely for what it was. He loved hitting, and he loved pitching.
For Ohtani, baseball was simply something he loved deeply. That is why he wanted to become a professional baseball player — so that he could continue playing the game he loved. And because he loved baseball so much, he did not want to limit himself to Japan. He wanted to challenge himself at the highest level, which led him to pursue a career in Major League Baseball.
Source
This quote comes from a Japanese book published in Japan and is not currently available in English.
『道ひらく、海わたる 大谷翔平の素顔』P50
(Opening a Path, Crossing the Ocean: The True Story of Shohei Ohtani), p.50