When did he used this: Boil release
the chapter before last... he uses chakra from 6-tail to melt the ice that was binding him, trying to make kaguya believe that he was stuck; but then used steam release to free himself.
the chapter before last... he uses chakra from 6-tail to melt the ice that was binding him, trying to make kaguya believe that he was stuck; but then used steam release to free himself.