The battle with Sato made Ye Tianchen all the more aware of the importance of increasing his strength; perhaps there were no Emperor Level experts on Earth, but there definitely were many hidden experts.
Sato, a top ten elder of the Kitashin One Sword Style, certainly had real strength that was no less than Ye Tianchen's. During the great battle, Ye Tianchen went all out and nearly tapped into the power of the Emperor Level Realm, but still failed to kill Sato, which was a testament to Sato's strength. Sato's death was almost self-inflicted; when he injected the first gene mutation drug, his power increased tremendously, almost to the point of overpowering Ye Tianchen. Had it not been for Ye Tianchen's use of his forbidden skill "Golden Eyes" to pierce Sato's heart, Sato might not have gone mad and swallowed a handful of gene mutation drugs.