Merely through a brief probing, Chen Xuan was able to test Tsukahara Isshin's strength, and it was definitely more terrifying than all the experts he had ever encountered before!
In fact, there are no strictly defined levels of mastery in this world. In the secular martial arts world of China, terms like Dark Force, Transformation Force, Qi Realm, and Grandmaster are simply classifications passed down by domestic martial artists based on the experiences of their ancestors. But once outside this circle, these boundary divisions cease to be universally applicable. The Ancient Martial Arts Realm is the same, except that ancient martial arts are almost unknown to the outside world.
As for the Security Bureau and the United States Department of Metahumans, their simple classifications of metahumans and transcendents into Tier One and Tier Two are merely definitions created by the organizations themselves. For instance, the Security Bureau classified Tsukahara Isshin as a Tier Four transcendent, but in reality, they had no idea what level Tsukahara Isshin's actual realm had reached. Furthermore, the Security Bureau also designated Chen Xuan as a Tier Four transcendent, yet Chen Xuan's peak capability far exceeded that of a Tier Four transcendent.
Chapter 1517