7 years have passed since Ultraman Tiga fought his final battle. Mankind has started colonizing the "new frontier," which includes Mars. The Terrestrial Peacable Consortium (TPC) is still around, with their main defense force now called Super GUTS. The current members of the team include Captain Hibiki, Kohda, Ryo, Kariya, Nakajima, and Mai. Super GUTS is recruiting new members, including Shin Asuka (pronounced more like "Ahs-kah"), a flighty, somewhat arrogant individual who, nonetheless, is one of the best pilots and marksmen they've found. His teamwork skills, however, leave much to be desired.

As part of the entrance exam, Asuka and his fellows engage in a mock battle in space. They are in older-style GUTS Wings, while Ryo and Hibiki are in upgraded GUTS Wing vehicles. As each trainee is hit, they are required to leave the battle. Asuka manages to evade both testers, scoring hits on both of their vehicles.

At that moment, a large glowing sphere appears nearby. It splits into multiple smaller spheres, and begins attacking the nearby space station and the smaller craft. Ryo's weapons jam after taking some damage, but Asuka rescues her. In the process, though, his ship is destroyed, though Asuka manages to get his breathing mask on in time to eject. He sees the sun appear from behind the Earth, and remembers the loss of his father, another TPC pilot who was lost while investigating an "unknown light." Suddenly a twinkle of light appears near Asuka. It grows into a large tunnel of blinding light, enveloping Asuka.

Asuka suddenly awakens in a bed in the new TPC headquarters, tended by the vivacious Mai. He has been accepted into Super GUTS, but must spend more time training after he recovers. While he recuperates, he has two vivid dreams. One involves a large 3-legged monster attacking the Mars colony, which is currently under construction. The other brings him back floating in space, encountering the tunnel of light.

Asuka is discharged, and is allowed to join the team. Their first mission is to deal with a large 3-legged monster attacking the Martian colony. They rush to the scene in a 3-piece vehicle equipped with Maxima Overdrive, the photon drive the original GUTS team used in their spaceship ArtDessei, and in their smaller craft, Snow White. (This was the craft used to try to revive Ultraman Tiga's stone form.) They battle the monster, but Asuka, always ready to leap before looking, manages to damage his craft and his co-pilot. Enraged, he begins firing at the belly of the monster with every hand-gun he has, but to no avail.

Suddenly, he is surrounded by a nimbus of light. He panics, but soon his body begins to grow. The light solidifes into a large Ultraman figure. Some of the older members of the TPC contingent in the colony believe it is Ultraman Tiga, returned and renewed. The elder officers, however, realize that it isn't Tiga, but may be another guardian like him.

Through the first 3 episodes, we see Asuka mature, realizing fully his responsibilities as a Super GUTS member, and as the human host of Ultraman Dyna (so named by Mai).

Unlike Daigo and Tiga, it seems Ultraman Dyna is a separate entity, much like most of the other Ultra-heroes. There appears to be some relationship between Dyna and Asuka Shin's lost father, but as of this writing that relationship has not been revealed.

Asuka is given a device, the Re-Flasher, to instigate the change, but it doesn't always work. On the other hand, there are times when he finds the change happening without his conscious knowledge. (This is how he changes in the first 4 episodes; the Re-Flasher doesn't work at all.) After the first half-dozen episodes, Asuka seems to need the Re-Flasher to change; in one situation where he loses the device, he cannot change until a couple of kids who find it return it to him. In many ways, this series reminds me of The Return of Ultraman, where Hideki Goh tries to change into Ultraman Jack, but cannot without Ultraman's permission. In one episode, Dyna discovers how to throw a fast-ball after Asuka learns the same; then again, we saw similar things happening with Hayata and Ultraman.

Ultraman Dyna, like Ultraman Tiga before him, has 3 forms. His Flash form, equivalent to Tiga's Multi type, has a balance of characteristics, including the Solgent Beam, fired much like Ultraman's Specium Beam. His Miracle form has great speed and telekinetic powers, including the Revolium Wave. His Strong form, obviously, is built for strength; he has fewer energy powers in this form. (Early reports indicated Dyna had no energy powers in Strong form, but episodes in mid-to-late season showed he does indeed have limited energy powers in that form.) One interesting difference with Dyna is that his 3 forms are more than mere color changes; the entire design of his torso (or costume) changes as well. Another difference from Tiga is that Dyna cannot change directly from Strong (red) to Miracle (blue) types without changing to Flash type first. (Tiga could go directly to any type/form from any type.)

Dyna, like the other Ultra-warriors, has a ColorTimer, or "warning light," on his chest. Changing forms tends to expend energy; in at least one instance, the transformation itself caused the light to begin blinking red. Early reports indicated that Dyna would "never rise again" if his ColorTimer were to stop blinking. However, one episode seemed to show him reverting to Asuka when this happened. (As he was being hurled through the air when this happened, it was hard to tell if Dyna simply changed back or if his timer ran out.) Dyna is able, under rather unique circumstances, to recharge his ColorTimer; in one episode, he fired a beam at a specially-constructed spacecraft which rebounded a beam that recharged him. This same beam later destroyed the monster he was fighting. In the movie Ultraman Tiga & Ultraman Dyna, Dyna's ColorTimer goes out, and Dyna apparently dies (although Asuka is still alive "inside" -- or wherever he goes when he transforms to Dyna). After Tiga is remanifested (see below), Dyna is recharged, once again proving that even a dark ColorTimer can't keep a good Ultraman down.

About 8 years after Tiga's time, another alien threat threatens the world. Ultraman Dyna overcomes the robot taken over by the aliens, but the aliens merge with their spaceship, forming a gigantic multi-tendrilled monster that traps Dyna and kills him. The city's population, in shelters much like they were during Ghatanazoa's attack, are motivated by a young boy who is a Super GUTS fan, but is a Tiga fan. Through his desire, and that of numerous others in the shelter (including the TPC scientist who, possessed by the aliens, created the robot), their life-forces remanifest Tiga. (Many of these kids remembered doing the same thing to revive Tiga during his final battle.) Tiga recharges Dyna, helps him escape from the monster, and the two Ultramen defeat the aliens once and for all. At the end, Tiga and Dyna transform into energy, and seem to merge.

Dyna meets his end when the Gran-sphere, an intelligent entity that pestered Dyna from the beginning, manages to create a giant hole in space, somehow related to the Neo-Maxima hyper-light drive that allows Super GUTS to travel between planets. The entity wishes to consume the entire solar system. In the process, Asuka's compatriots learn that he is Dyna. The team forms a plan to fire a Neo-Maxima-based weapon into the hole, which reveals the Gran-sphere at its core. Dyna then fires his Solgent Beam before the hole can "heal." The Gran-sphere and the Neo-Maxima hole is destroyed, but Dyna is caught in the collapse, disappearing forever. While Super GUTS mourns the loss of their comrade, as a new Ultra-star shines, Asuka finds himself flying alongside his long-lost father, still in his Zero-Drive ship, heading together towards the light.

A movie released in the spring of 1999, Ultraman Tiga, Ultraman Dyna, & Ultraman Gaia will allow Dyna and Tiga to meet Ultraman Gaia, even though they are not set in the same universes.