Byakugan and Gentle Fist

Itachi felt like that basically made sense. If you followed Mukai’s
bloodline back, you reached the Hyuga clan, one of the most distinguished
families in Konohagakure. If you traced the origins of the Hyuga, you arrived at the founder of the ninja, the Sage of the Six Paths. And the Byakugan kekkei genkai was a visual jutsu on par with the Uchiha sharingan. The Hyuga could see the path of chakra circulating in the body and seal chakra by severing the pathway in someone who had become an enemy.

Their vision was also said to reach out in all directions, with no blind spots. Once the pathway was sealed, the Hyuga clan used physical techniques.

Their physical jutsu, known as Gentle Fist, aligned the flow of the user’s chakra with the chakra extant in all living creatures, allowing the user to deliver a series of blows based on circular defensive movements, destroying anything inside their opponent’s body, such as internal organs.

Gentle Fist was a secret of the Hyuga clan, but given that they were a branch family, it
was no stretch to imagine that at least some knowledge of it had been passed
down to the Kohinatas.

Itachi Shinden: Book of Bright Light Chapter 3 Part 4