Yantsu has been translated as ("safe three" or "safe in three ways"), using the characters of Yan - 安, meaning "safe", and Su - 三, meaning "three". Three is significant in Buddhist teachings and included in many other Kata names and methods, such as San Chin.
Yantsu is an old Kata with unknown origins,but perported to be from the Naha-te and/or Tomari-te Karate traditions. It is primarily used by Kyokushin and a slightly longer variation is found in Shito-ryu as Ansan. It is speculated that it Mas Oyama learned the Ansan from Shogo Kuniba sensei (Shito-ryu) and imported it in a shorter version and with a few modifications, into Kyokushin. Oyama adapted the Kata to the Kyokushin system, with its own modes and techniques, where more emphasis is placed on strength.
Here Sandan Saghi Ownjazayeri, works Kyusho into self defense bunkai, first explaining the targets and tools and adapting them for more dynamic applications.