When the internet became widely accessible in the 1990s, it opened up new opportunities for people who had previously been limited by geography or financial constraints.
The arrival of YouTube further transformed learning, allowing anyone to study not just by reading or listening, but by watching.

This shift was especially significant in sports.
With nothing more than a computer and an internet connection, athletes could repeatedly watch the movements of the world’s best players anytime they wanted.

Shohei Ohtani was no exception.
After a computer arrived at his home, he began spending countless hours watching YouTube, studying different pitching styles and thinking through what he saw.

For hitting, he paid close attention to the timing of Toshiaki Imae.
For pitching, he learned from the windup of Daisuke Matsuzaka, and also studied the mechanics of Kazumi Saito and Yu Darvish, often imitating their forms.

Whenever something clicked, Ohtani would slide open the shoji screens and check his form by watching his reflection in the window.
Even after becoming a professional, he maintained the same habit — whenever he had an idea, he would go straight to the field and try it out.

For Ohtani, watching meant thinking,
and thinking meant experimenting.

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.262