Xu Shu's title [Sit-ups] is a heavily restricted ability.
It carries no killing power, and its application conditions are extremely harsh. One must be in the midst of "continuously doing sit-ups" to gain the effects of a life source and immunity below the taboo level.
When he is bound, pinched, or simply knocked unconscious and controlled by various means, this title becomes completely useless.
In other words, this ability, when facing an enemy stronger than oneself, merely grants a little extra time to linger on.
In actual combat, it almost rarely works.
An enemy stronger than you won't watch you recover your stamina.
Still, despite such big limitations, to Xu Shu, "Sit-ups" remains his most valued ability, bar none.
It's not an exaggeration to say it's the foundation of his existence.
