Shohei Ohtani joined the Mizusawa Little League in the second grade of elementary school.
Most of his teammates were older boys, but because he had been playing catch with his father, older brother, and mother from an early age, he already had a solid foundation — he could throw and hit at a reasonable level from the start.

There were, of course, physical differences between him and the older players.
Even so, as time passed, Ohtani gradually became able to compete on equal footing — and eventually beyond — with children older than himself.

While many of the others needed a running start and one or two bounces to reach certain distances, Ohtani learned to throw the ball without a running start and without letting it bounce.
His hits also began to travel farther than those of his peers.

According to Ohtani, the confidence he had from the beginning — the sense that he was at least slightly better than those around him — continued to build over time.
That growing confidence led directly to a stronger desire to improve and become better.

For a child, an early sense of confidence can be extremely important.
In Ohtani’s case, that initial confidence became the foundation upon which everything else was built.

Source

This quote comes from a Japanese book published in Japan and is not currently available in English.

Shohei Ohtani: Baseball Soaring Years I – Japan 2013–2018, p.259