WARNING: The following contains major spoilers for The Rise of Ultraman #5 by Kyle Higgins, Mat Groom, Francesco Manna, Espen Grundetjern and VC's Ariana Maher, on sale now.
The Ultraman series has seen a multitude of heroic humans take up the mantle of the titular hero since it was first introduced in 1966, even if Ultraman himself wasn't properly introduced until the second season of the original show. While Marvel's The Rise of Ultraman is a departure from many of the typical trappings that the franchise is known for, it's also made mention of one of the very first Ultra heroes as an important part of its mythos. Dan Moroboshi has been missing for decades, but thanks to Shin Hayata he has finally made his way home after years of being trapped in Hell.
USP Cadet Kiki Fuji went searching for answers regarding the organization's secrets, and in doing so ended up trapped in the same Limbo dimension that Kaiju are transported to by the USP's K-Ray weapons. Once the truth of the matter had been revealed, Shin Hayata took it upon himself to go rescue his friend as Ultraman. His short time in Limbo uncovered some terrifying facts about the USP's operations so far. Once Shin and Kiki arrived back on Earth, they realized that something followed them home, and Ultraman was forced to fight a towering Kaiju while running down the clock on his powers. With the threat of a Kaiju prison break looming over the near future, Shin determines that the only way to win is to open the interdimensional floodgates and let the monsters loose on Earth where they can be permanently disposed of. It's a risky move, but one that is ultimately the only sound option the heroes have left.
It doesn't take much convincing for Shin to be allowed to go through with his plan. In his Ultraman form, Shin tears through the veil between our world and Limbo in the hopes that a controlled release of the Kaiju in relatively unpopulated areas of the world will not only give him a chance to stop them once and for all but will also give the USP a chance to come clean to the world in a way that they won't be regarded as another dangerous organization operating out of the shadows by the public. Unbeknownst to Shin and his allies, Kaiju weren't the only ones trapped in Limbo, and he's just freed one of the series most well-known characters from a waking nightmare.
Somewhere in New Zealand, Dan Moroboshi stumbles into a general store, knocking over a produce display when he collapses through the door. His clothes are tattered, and he has no idea where he is. He might not even know when he is, considering how long he has been missing. Dan Moroboshi was one of the USP's best agents, and the first man to come into contact with an Ultra in the same way that Shin did all the way back in 1966. While the United Science Patrol officially assumed that Dan was killed in his encounter with the alien, that is clearly not the case. Whether he has merged with the Ultra he encountered the same way that Shin has is yet to be seen, but wouldn't be unexpected considering the character's history.
Dan Moroboshi was first introduced in 1967's Ultraseven television series by Tsuburaya Productions. Played by Kohji Moritsugu, Dan was the sixth member of the Ultra Guard, an elite squad dedicated to keeping the world safe from extraterrestrial threats. Originally, the character was an alien who came to Earth and assumed the form and name of Dan Moroboshi in order to pass as human.
His Ultra form became known as Ultraseven, in reference to it being the unofficial seventh member of the Ultra Guard, and as both Dan and Ultraseven he was instrumental in protecting Earth from the forces of evil. This version of the character hasn't always stuck around, often venturing back to the cosmos for other adventures, but has still made frequent returns throughout the years. Even throughout all of the various versions of the character, Dan Moroboshi has always been one of the most intriguing and memorable characters in the Ultraman universe. From the looks of things in Marvel's own take on the series, that doesn't look like it's changing any time soon.