I've heard multiple people say that in order for someone to unlock Susano'o, that person or persons must acquire Amaterasu and Tsukuyomi beforehand in order to achieve it. I've never seen Madara use Amaterasu, yet he has PS. Shisui has Susano'o, yet Kishi has never had him use Amaterasu or Tsukuyomi. Is it true that you don't need Amaterasu and Tsukuyomi to unlock the Susano'o, but just both MS eyes?