Whose idea was this? This is one of the worst ideas I've ever heard.
Ninjas can cast ninjutsu while moving normally, so why not during Ten Chi Jin? It runs counter to years worth of muscle memory and has no base in flavor or balance. "Here, we'll give you your level 70 ultimate skill, it uses up your whole gauge and by the way it takes 4 seconds to cast and if you have to dodge anything you lose it all, ninki gauge, cooldown, and everything!"
SE pls.