S1·E11 A Song You Still Don't Know About

Bocca and the team successfully saves Sayoko. Sayoko reveals to them that there are still people in Engine One. They decide to try and save them too. The Monster Union member is later defeated in battle, but reveals that the people aren't really 'humans' but have been turned into something better. Tsunagi, in his attempt to destroy Engine One from the control station, finds a recording of someone he knew and had thought betrayed him. The recording reveals some surprises. Bocca wants Tsunagi to leave the place with him before the whole place blows up, but Tsunagi insists on staying. The team leaves without Tsunagi, and Engine One blows up.