The user first allows himself to be hit by his opponent and follows the opponent's energy flow. Therefore, when the user gets hit, their body automatically bows down and gives the opponent a powerful headbutt. This technique basically uses the opponent's strength to counterattack.
The name "Sha Gi Shou Jin" is a Chinese phrase "捨己從人", it mean "sacrifice yourself to follow other". It English name were given by Diego Carlo. There is some argument about which should be it true name.