Friends Left Behind (残された仲間 Nokosareta Nakama) is the first Ultraman Ginga side story, continuing where episode 11 left off. Some time after Ginga and Taro return to space, Kenta and Chigusa will investigate the appearance of Alien Magma in Japan.
The episode begins with Kenta as the narrator, and the scene shifts to the moon, where Ultraman and Tiga are fighting against Zetton. He recalls the events that led to this battle happening.
After Ginga's departure from Earth, Alien Magma is seen warming himself beside a fire in Tokyo. He recalls how he was DarkLived into full form with Alien Valky, but Valky was chosen as Dark Lugiel's right hand instead of him, and Magma was made fun of. The same thing happened when Icarus and Alien Nackle Gray were picked, despite Magma training himself to be more useful to his master. Now all alone, Magma screams in despair.
The next day, Kenta is taking Chigusa out for a photoshoot. They remnicise about Ginga leaving Earth, when Kenta spots Magma loitering about, and decide to tail him. Eventually they bump into each other and Magma vents his frustrations on the two, saying that he has been unable to find a job, threatening to attack them. Kenta and Chigusa flee with Magma in hot pursuit.
Finally, when neither of them can run anymore, Magma corners them and whips out Zetton's Spark Doll. Kenta tries to grab it, but is kicked in the chest. Chigusa attempts to reason with Magma, but fails. Magma uses his dark powers to tap into Chigusa's negative emotions and forms a Dark Dummy Spark in front of her. Magma goads Chigusa into grabbing it, but Kenta prevents her from doing so, shattering the Dark Dummy Spark.
Cursing Kenta, Magma DarkLives into Zetton and prepares to destroy Tokyo. Kenta and Chigusa wonder what they can do in their current state, when suddenly, Ginga Light Sparks appear in their hands once more, and with them, the Spark Dolls of Ultraman and Tiga. They transform and force Zetton away from Earth and onto the Moon, beginning their fight.
Tiga and Ultraman fire their beams at Zetton, but he vanishes and attacks Ultraman from above. Ultraman blocks the attack, and Tiga manages to send Zetton flying with a kick, causing him to land heavily on the ground. Ultraman grabs Zetton and Tiga charges up his Zeperion Beam. But before Tiga can fire, Magma sneakily escapes from inside Zetton and strikes Ultraman from behind. Zetton and Magma strike at both Ultras, leaving their Color Timers blinking.
Zetton fires a fireball towards Earth, but Ultraman and Tiga use the last of their energies to take the attack upon themselves. They assert their determination to protect the Earth from Magma, Before he can land the final blow though, Ultraman Ginga reappears in the nick of time and blocks Magma's blade with Ginga Saber, before taking the fight to Magma and Zetton. Overpowering the aliens, he ends the fight with a powered up Ginga Cross Shoot.
Tiga and Ultraman's time limits are almost up, and Chigusa and Kenta panic, not wanting to die in space. Ginga gets to them in time and returns them to Earth.
- Kenta Watarai (渡会 健太 Watarai Kenta): Mizuki Ohno (大野 瑞生 Ōno Mizuki)
- Chigusa Kuno (久野 千草 Kuno Chigusa): Kirara (雲母 )
- Ultraman Ginga (ウルトラマンギンガ Urutoraman Ginga Voice): Tomokazu Sugita (杉田 智和 Sugita Tomokazu)
- Alien Valkie (バルキー星人 Barukī Seijin Voice): Tatsuya Hashimoto (橋本 達也 Hashimoto Tatsuya) (flashback)
- Alien Nackle Gray (ナックル星人グレイ Nakkuru Seijin Gurei Voice): Kunji Hirano (平野 勲人 Hirano Kunji) (flashback)
- Alien Magma (マグマ星人 Maguma Seijin): Koichi Toshima (外島 孝一 Toshima Koichi)
- When Alien Icarus calls Alien Magma, listen very closely to the ringtone - it is that of Ultraman Leo's first opening theme.