Ryoko is an amnesiac fake identity of Junko Enoshima. She was created after The Tragedy of Hope's Peak Academy, when Yasuke was asked to interrogate Junko about the incident. Instead, he reluctantly assisted Junko by testing procedures for memory-erasing in preparation for the Killing School Life of 78th Class. Having succeeded in erasing her own memories with Yasuke Matsuda's memory-erasing technology, Junko assumed the fake identity of Ryoko Otonashi and hid from suspicion.