Fundamentals

And thus, they immediately began training.

Rui had Ieyasu begin imparting a diverse variety of principles to him, starting from the most fundamental and universal fields.

"Breathing is a fundamental foundation of nearly everything I copy."

In a training chamber in the manifold meant for breathing, Ieyasu sat opposite Rui. The latter had a breathing training apparatus attached to his mouth and nose.

This was an apparatus that not only trained breathing strength but also breathing patterns.

Different patterns of breathing corresponded with different rates of oxygen supply to the body. It was this principle that was the basis of supplementary breathing techniques.

Additionally, breathing techniques were also at the foundation of heaven manipulation, which was another popular field in Martial Art.

Thus, as long as he gained a foundational mastery of his breathing, he would automatically gain a lot of potential variety and power.