Episode 20, "Grudge! The Longest Day at Kurogane House: Part 2"
Synopsis: As Kouji in the Mazinger battles what seems to be his father in the Energer Z, Tsubasa recalls the events that led to the death of Tetsuya Tsurugi. It's revealed that Kenzo Kabuto was a Dr. Hell sympathizer and planned to join him in his plans to take over the world with the Mechanical Beasts. With the help of Zeus' hand, Tetsuya managed to pin down the traitorous Kenzo just long enough for Tsubasa to fire at him. In present time, Tsubasa confronts "Ashura", really Pygman in disguise, but is ready nevertheless to reveal the location of Zeus' hand.