Shohei Ohtani began playing baseball with the Mizusawa Little League and reached the national tournament in his first year of middle school.
He later advanced to the national stage again with the Ichinoseki Little Senior team.

Around that time, Hanamaki Higashi High School in Iwate was making headlines at Koshien, led by pitcher Yusei Kikuchi.

After losing a game at the national tournament and finding themselves with unexpected free time, the Mizusawa team faced a choice.
They could either go watch the ongoing Koshien games, or visit Hanamaki Higashi to observe a practice session.

For most young players, watching games at Koshien would have been the obvious choice.
But as team captain, Ohtani chose to visit Hanamaki Higashi’s practice instead.

What he saw left a strong impression.
“When I watched their practice, I felt it was right,” Ohtani said. “The atmosphere was good.”

When young players consider where to continue their careers, they often focus on whether a school can take them to Koshien.
Ohtani believed that was important, but not the most important factor.

What mattered more to him was whether the environment would allow each player to grow and develop as an individual.
At schools with large rosters, training opportunities can be uneven.
Hanamaki Higashi’s practices, however, were efficient and designed to help every player improve.

Through his experiences in Little League and Senior League, Ohtani had come to believe that Iwate had many talented players.
If they came together in the right environment, he felt they could aim for the top.

That belief led him to choose Hanamaki Higashi High School,
where he set out to pursue a national championship with fellow players from his home prefecture.

Source

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

Baseball Soaring Years II – MLB Edition 2018–2024: Long Interview with Shohei Ohtani, p.83