Board Thread:General Discussion/@comment-24518534-20140207202148/@comment-11051098-20140208192424

Renji and Yumichika are the only ones who knows that Ikkaku has Bankai. Well, after Poww's defeat, Tetsuzaemon mentioned Ikkaku's Bankai, so he apparently knows too, and Sajin appeared to overhear him mentioning it. But this was long after Ikkaku used his Bankai to defeat Edrad.