Every three million years, the Solar System passes through a place called the Unbalanced Zone. At the dawn of the 21st century, as the Earth's population rises, the Solar System passes the Unbalanced Zone once again, where Dark Matter starts the appearance of monsters. Genki Kagura of the Hi-Tech Earth Alert and Rescue Team (HEART) is working with a space team when meteorites pummel a satellite that's being operated on. Kagura saves the team just as the satellite explodes, ejecting him into space. Miraculously, he survives and later rejoins his team to investigate a rockslide incident that might be related to the appearance of Japan's first monster.
When the monster, Aranagaruge, appears with Nana Hayami, a child, and his dog endangered, Kagura must access the memories he lost while drifting through space and learn the origin of his survival. He would later fight monsters made of Dark Matter, occasionally assisted by Ultraseven 21 (Pronounded "two-one").
Ultraman Neos was originally supposed to be the back-to-basics entry that revived the Ultra Series in the Heisei era. Since the network wished for a more original series, Ultraman Tiga was created. Most of the ideas brought up in the pilot were used for Tiga, Dyna, and Gaia, so Neos felt a bit So Okay, It's Average by the time it was released.
Ultraman Neos provides examples of the following tropes:
- A God Am I: Mensch Heit believes himself to be the Ultimate Lifeform, and that, as in his mind mutation is the will of the universe, that makes him the living embodiment of its will and has the right to do whatever he wants. He's even called out for thinking he's a god.
- Alternate Universe: Despite the appearance of Zoffy and M78, Neos takes place in a different universe.
- Anti-Villain: Alien Zamu, whose very planet and culture was destroyed by Dark Matter, and every appearance has them being the cosmic playthings to the Unbalanced Zone.
- Arbitrary Skepticism: Takayoshi Hino's initial doubt about monsters, even though one of HEART's major purposes is to deal with such threats in the first place.
- Beam-O-War: The final battle ends with Neo's Neo Magnium Ray and Ultraseven 21's Rejia Shot vs Mensch Heit's final attack. After a struggle, they manage to push through and blow him to bits.
- Be Careful What You Wish For:
- The kids who wish to keep a dinosaur roller coaster ride open try to spread a rumor of a dinosaur monster to HEART. They next try to create a monster of their own. By the stroke of luck of Dark Matter, the creation of King Dinas unwittingly get their wish.
- Mensch Heit demanded the last Alien Zamu to be killed in exchange for Earth's safety. Esura did lost his life, but through a Heroic Sacrifice by recharging Neos and Seven 21's energies, which lead to the villain's death and finally Earth's own peace.
- Beware the Nice Ones: Bamos is a friendly, affectionate ape-like creature... until you hurt his loved ones, in which case he grows into the Ax-Crazy King Bamos and electrocutes you to death. There's a reason he's the top dog on the island.
- Bridge Bunnies: Ayumi Kitabayashi. Other times, she's being The Smart Guy.
- The Cameo: Zoffy gets one.
- Expy: Bamos is clearly reminiscent of the classic Pigmon... except for the part where he is a Sizeshifter and the King of the island of monsters.
- Final Solution: Mensch Heit wants the Alien Zamu dead, and his entire reason for arriving on Earth is to kill off the survivors. He succeeds, but not before Esura gives humanity the archive of his species' DNA to perhaps revive them someday.
- Fun with Acronyms: Hi-Tech Earth Alert and Rescue Team.
- Green Aesop: The episode with the monster Lefreshion plays the aesop in an interesting manner. While the monster can heal plants, the healing bubbles are poison to humans. This wouldn't concern the girl who thinks she's controlling him — except for the part where all the other animals are also negatively affected.
- Heroic Sacrifice: Esura sacrifices himself to restore and empower Neos and Ultraseven 21 to defeat Mensch Heit once and for all.
- Hidden Depths: Secretary Yoko Fujiwara, a liaison between HEART and the government, initially comes across as a "Stop Having Fun" Guys Obstructive Bureaucrat. However, her friendship with Dr. Otome and her manhandling of an even greater Obstructive Bureaucrat shows she's loyal to the team.
- Mythology Gag: The Unbalanced Zone's name is a reference to Unbalance, the planned title of Ultra Q before it was changed.
- Parental Abandonment: Ayumi lost her parents while she was in college.
- Sizeshifter: Bamos to King Bamos when you piss him off, and Ultra Seven 21.
- Twelve Episode Toku plus one OVA.
- Ultimate Lifeform: Mensch Heit believes himself to be this, and thus having the right to do whatever he wants.
- Voluntary Shapeshifting: Ultraseven 21 is a rather unique Ultra in that he doesn't have a standard human form or host, but assumes numerous forms throughout the series.