Levi felt that the reason for this phenomenon might be because the attribute of strength was the greatest boost to combat power.
As the saying goes, strength could break all techniques. This caused the mainstream breathing technique to become a strength.
As for the other three breathing techniques, one of them was a shallow-quality breathing technique that Levi was not too interested in at the moment.
There were only two breathing techniques that interested him.
One of them was called the 'Undying Bird Breathing Technique'. It was actually an extremely rare perfect-grade breathing technique, and it was even a relatively rare type of physique.
The other book was the 'Night Owl Breathing Technique'. Although it was only of a shallow quality, it was a very rare Perception technique.
"This Andrew is really good at doing things. In the future, I should give him the title of an excellent employee."
He was in a very happy mood.