S1·E16 Kei: A Song of Farewell
Aired July 11, 1978
Synopsis
The operator, Kei Yuki, goes to visit her parents' grave. There, her father's ex-pupil, Kazuya, shows up. They had attempted to make a space colony not out of machines, but with nature exactly akin to Earth's. However, the experiment failed and Kazuya, the lone survivor, returned to blame her father.