Dark Side (ダーク サイド Dāku Saido) is one of the Ultraseven 35th Anniversary: EVOLUTION episodes of Heisei Ultraseven.
Five years had passed since the Omega Files incident. Kazamori had since retired from being an Ultra Guard member and visited Satomi at her holiday villa. He admitted that he had no knowledge of what happened when Seven masqueraded as the former and is currently feeling a sense of loss with the Ultra’s departure from Earth. For his crimes in interfering with the human-Nonmalt war, Seven was sealed at the Horse Head Nebula by the entire universe itself.
At some point during Seven’s departure, mankind received a peace treaty from the entire universe, giving assurance that Earth will not be invaded while TDF prepared for their arms reduction and Ultra Guard to be disbanded. UG was introduced to a new team member named Yuki Kisaragi, who was previously a member of the special force. Alongside Rumi, Yuki was sent to investigate a gravity anomaly in a particular location and discover an Alien Pegassa. Despite the alien’s non-aggression approach, Yuki’s hasty firing caused the former to retaliate by sending Rumi to the Dark Zone. Back in her early days as a special force officer, Yuki was rendered unconscious after an alien attack, causing her to attack any of them on the spot due to the aforementioned trauma. Unaware to the UG officers, she constantly reported her actions to TDF staff officer Inagaki. Mizuno discovered a strange device made from the same metal from Pegassa City and finally connected the dots that Alien Pegassa was the perpetrator.
Yuki paid her visit to the orphanage she was raised in (which happened to be in the same vicinity in the crime scene) and told her caretaker, Sayuri, to take the children away for safety. Shiragane discussed this matter with TDF officers Saijou and Inagaki, the latter decided to keep the Pegassa’s case a secret from the civilians. As Saijou’s men drove Shima and Yuki away from the crime scene, Satomi returned to her duty as a UG officer. Meanwhile, a pair (Tashiro and his junior) of TDF researchers discovered muons coming from outer space.
Satomi and Yuki lured Saijou’s men away from the crime scene through a diversion. The Dark Zone reappeared to drag Satomi into it, while Yuki was injured and forced to flee from the scene through Kazamori’s arrival. A lone Pegassa revealed that his action was done so as to avenge those who were killed in Pegassa City by taking Earth as their replacement home. After discovering that Kazamori had no idea as to why the alien would go as far as to reveal his motive, the alien quickly realized too late that the young man was not Seven and was quickly killed by Saijou. Kazamori advised Saijou not to trust other members in TDF, especially since his own men were killed and replaced with impostors.
Kazamori met Sayuri while tending Yuki’s injury, having been summoned to the orphanage via telepathy. Meanwhile, Satomi reunited with Rumi in the Dark Zone to discover the a rather peaceful Alien Pegassa explaining what happened in the incident; after the destruction of Pegassa City, the surviving members split into two factions, the radical group who sought to overthrow mankind for the ownership of Planet Earth and the moderate faction who lived peacefully with the human society. This benevolent Pegassa had a leader (Sayuri) who ran an orphanage to take care of children who suffered the same misfortune as they did. The radical faction had been preparing their invasion for years to weaponize the Dark Zone into devouring an entire city block into an alternate dimension. Sayuri confessed to Satomi that after being force to abandon her own children in Pegassa City, she founded the orphanage to atone for her mistake. Yuki was one of those children she cared for after the latter was tormented by her abusive parents, going as far as to join TDF to protect the orphanage in return. Discovering her caretaker as an alien, Yuki became hesitant to kill her due to the times the spent together.
Kazamori slipped into the Ultra Guard headquarters to steal the device for Sayuri, arriving on time to prevent her (as well as Satomi and Yuki’s) assassination from a radical Pegassa member. The device was one of the component of a device used to destroy the weaponized Dark Zone, as it was hunted down by the radical Pegassa faction and a few of the moderate Pegassa even sacrificed themselves to protect it. When the Dark Zone started to appear, Saijou can only hope for Ultra Guard’s assistance. Sayuri choose to sacrifice herself by entering the Dark Zone and activated the neutralization device at the cost of her own life. In her final moments, she revealed to Kazamori that the answer to his problems lies in the currently imprisoned Ultraseven. After Sayuri’s death, a strange saucer-like creature appeared in the sky.
Yuki decided to abandon her contact with Inagaki, while the source of the muon was traced to the same location where Seven was imprisoned.
- Masaki Kazamori (カザモリ・マサキ Kazamori Masaki): Katsuyuki Yamazaki (山崎勝之 Yamazaki Katsuyuki)
- Sanshiro Shiragane (シラガネ・サンシロウ Shiragane Sanshirou): Koji Nanjo (南条弘二 Nanjo Koji)
- Keisuke Shima (シマ・ケイスケ Shima Keisuke): Kunio Masaoka (正岡邦夫 Masaoka Kunio)
- Takuma Mizuno (ミズノ・タクマ Mizuno Takuma): Wataru Koga (古賀亘 Koga Wataru)
- Satomi Hayakawa (ハヤカワ・サトミ Hayakawa Satomi): Kaoru Ukawa (鵜川薫 Ukawa Kaoru)
- Rumi Honjou (ホンジョウ・ルミ Honjou Rumi): Rieko Adachi (あだち理絵子 Adachi Rieko)
- Yuki Kisaragi (キサラギ・ユキ Kisaragi Yuki): Mika Katsumura (勝村美香 Katsumura Mika), Saki Amagai (天貝早希 Amagai Saki) (young)
- Inagaki (イナガキ Inagaki): Masahiro Noguchi (野口雅弘 Noguchi Masahiro)
- Saijou (サイジョウ Saijou): Masaki Nishimori (西守正樹 Nishimori Masaki)
- Suwa (諏訪 Suwa): Kyoji Kamui (神威杏次 Kamui Kyoji)
- Tachiro (タシロ Tachiro): Tomokazu Seki (関智一 Seki Tomokazu)
- Narrator (ナレーター Nareta): Kohji Moritsugu (森次晃嗣 Moritsugu Kōji)
- Alien Pegassa (ペガッサ星人 Pegassa-seijin) leader (Voice)/Teacher Sayuri (サユリ先生 Sayuri-sensei): Hiroko Sakurai (桜井浩子 Sakurai Hiroko)
- Murakami (ムラカミ Murakami): Naoki Ichimura (市村直樹 Ichimura Naoki)
- Teacher Hiroko (ヒロコ先生 Hiroko-sensei): Mariko Mizutani (水谷真規子 Mizutani Mariko)
- Alien Pegassa (ペガッサ星人 Pegassa-seijin) (Voice): Masaharu Satō (佐藤正治 Satō Masaharu), Hiroki Tonomura (外村ひろき Tonomura Hiroki)
- Ultraseven (ウルトラセブン Urutorasebun): Satoshi Yamamoto (山本諭 Yamamoto Satoshi)
- Alien Pegassa (ペガッサ星人 Pegassa-seijin): Hiroki Tonomura (外村ひろき Tonomura Hiroki)