Battle! Monster Island (激闘! 怪獣島 Gekitō! Kaijūtō) is the sixteenth episode of Ultraman Dyna.
One day, Asuka and Nakajima visit Hanejiro in the TPC Biotechnology Research Institute. The scientist who had been studying Hanejiro was one Dr. Ootomo. While the two Super GUTS officers play with the creature; Yamazaki, the doctor's assistant, informs his teacher that he has been ordered to appear before the South Europe branch's court of inquiry.
The next day, Super GUTS discover that Ootomo had fled in his personal plane along with Hanejiro. Officers Kohda, Ryo, Kariya, Nakajima and Asuka dispatch in the GUTS Eagle and head towards the Zariina region, a zone with an intense magnetic field. Gamma is ordered to stay on aerial standby while Asuka, Kohda and Nakajima press forward in Alpha and Beta. The three find themselves on an uncharted island. Suddenly, the kaiju Sildron and Silvergon appear and begin to brawl. After a short scuffle, the silver beast crushes the life out of the insect kaiju using its tail.
After Nakajima scares Silvergon away by shooting its eyes, the trio spot Yamazaki spying on them from a distance. Super GUTS give chase. They manage to catch Yamazaki, who escorts Kohda and Nakajima to the doctor's laboratory while Asuka returns the the Eagles. Dr. Ootomo greets the pair upon their arrival. He reveals his plan: to create clone kaiju in order to advance the Neo Frontier. Now he plans to extract Hanejiro's intelligence genes and insert them into Hyper Clone Kaiju Neosaurus - thus creating the ultimate kaiju.
But before he can continue the extraction, Asuka, in Alpha, blows apart the wall of the lab. However, in doing so he attracts the attention of the clone Silvergon. Ootomo quickly escapes and deploys Neosaurus in order to defend the lab. The two beasts duel but Silvergon is no match for Neosaurus' pure brawn; and is quickly defeated by the Helix Beam. In an act of proof of its lack of intelligence, Neosaurus kills Ootomo. Asuka attempts to attack the kaiju, but winds up getting Alpha destroyed. However, he was able to transform into Ultraman Dyna at the last moment.
From the beginning, it is clear that the Ultra was completely outclassed by the chimera kaiju's sheer strength, and he is quickly placed in a tough situation. This prompted a transformation into Strong Type to even the playing field. But even in Strong Type, Dyna was still only barely keeping up with Neosaurus' power. Using its own Helix Beam against it, Dyna manages to amputate the kaiju's tail before finishing it off with the Garnate Bomber.
Afterwards, Nakajima and Kohda mourn the deaths of Dr. Ootomo and Asuka. At that moment, however, Asuka reveals to still be alive - claiming to have ejected in the nick of time. The three relax after the long day and play with Hanejiro on the island.
- Shin Asuka (アスカ・シン Asuka Shin): Takeshi Tsuruno (つるの 剛士 Tsuruno Takeshi)
- Gousuke Hibiki (ヒビキ・ゴウスケ Hibiki Gōsuke): Ryo Kinomoto (木之元 亮 Kinomoto Ryō)
- Toshiyuki Kouda (コウダ・トシユキ Kōda Toshiyuki): Toshikazu Fukawa (布川 敏和 Fukawa Toshikazu)
- Ryo Yumimura (ユミムラ・リョウ Yumimura Ryō): Risa Saito (斉藤 りさ Saitō Risa)
- Kouhei Kariya (カリヤ・コウヘイ Kariya Kōhei): Takao Kase (加瀬 尊朗 Kase Takao)
- Tsutomu Nakajima (ナカジマ・ツトム Nakajima Tsutomu): Joe Onodera (小野寺 丈 Onodera Jō)
- Mai Midorikawa (ミドリカワ・マイ Midorikawa Mai): Mariya Yamada (山田 まりや Yamada Mariya)
- Dr. Ootmo (オオトモ博士): Miyazawa Akira (宮沢彰 Akira Miyazawa)
- Hiroyuki Yamazaki (ヤマザキ・ヒロユキ Yamazaki Hiroyuki): Watanabe Yushi (渡祐志 Yushi Watanabe)
- Ultraman Dyna
- Flash Type
- Strong Type
- Ultraman Dyna Volume 4 features 13-16.
- This episode was later featured in episode 49 of Ultraman Retsuden, "Fierce Battle! Dyna in the Monster Island!!".
- This episode is a tribute to the Ultraman episode, "The Mysterious Dinosaur Base".
- This episode marks the debut of the Garnate Bomber.