Shohei Ohtani chose Hanamaki Higashi High School not only because of its results, but because he felt the overall atmosphere and quality of training would help him grow as a player. Whether or not a school regularly reached Koshien mattered, but just as important to him was whether the environment could develop his abilities.

During his time at Hanamaki Higashi, Ohtani reached Koshien twice, but both appearances ended in first-round losses. While disappointing, his high school years offered something equally valuable. Living in the school dormitory and away from his family for the first time, Ohtani learned how to live in a communal setting and received guidance not only in baseball, but in daily life as well.

Up to that point, the person who had taught him most was his father, who had served as his coach in Little League and Senior League. Ohtani had learned many important things from him. However, he later reflected that even when the advice itself was the same, being told by someone other than a parent carried a very different meaning.

When parents say something, even if it is correct, children often dismiss it as familiar nagging. The same words, coming from a coach or teacher outside the family, can suddenly feel convincing and real. Ohtani recalls that being scolded by his high school coach forced him to think more carefully and act more deliberately—marking a clear step in his growth, both as a player and as a person.

Source

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

Baseball Chronicle II: MLB Years 2018–2024 – Long Interview with Shohei Ohtani, p.87