This was considered to be is a secret technique to escape from multiple attackers. The other name for this is 'Yamabiko-no-michi", the path of an echo.
As you extend your Ki, the Ki of your opponeent will return to you like an echo. However, you do not receive your opponent's Ki because you have instantly moved past him to his rear.
(Oral Instruction - an old poen taught to the student)
Brandishing his sword,
My enemy if front
Prepares to attack.
But behind him,
I am already standing.
Many ennemies
Surround me in attack.
Thinking of them as one,
I do battle.