[Crossover] Ultra Warrior, but He's Batman

Bruce opened his eyes. With the advice and help of a new friend, he walked among the living once more. To find his family and friends, he set off on a brand-new journey. But something went wrong as soon as he reached the first world. With little time to prepare, Bruce found himself face-to-face with a fifty-meter-tall monster attacking a city. Bruce: ? Knowing he wasn't that easy to kill, Bruce unhesitatingly used his body to shield a little girl from a huge chunk of falling debris. Just as he was calculating how to get the child to safety unharmed, a beam of light suddenly shot into his body. An alien who called himself Zero said he had been moved by Bruce's willingness to risk his life to save someone. He was also gravely injured, so he decided to merge with Bruce. Bruce: ?? Wanting to test the other guy's abilities, Bruce held back the urge to yell, "Get out of my body!" He followed the other's instructions and put on a strange pair of glasses, only to transform into another fifty-meter-tall giant. Bruce: ??? And so Bruce, once Batman and now traveling to find his family and friends, became the human host of an Ultra Warrior. With no identification whatsoever, he also ended up joining Earth's Defense Force. Bruce: ...Six. - At the risk of being pinned down by the Mother of Ultra and stuck in the Silver Cross Hospital for years, Zero once again brought his gravely injured self and a pursuer to Earth. After choosing a reckless guy who'd risked his life to save someone as his human host, Zero realized things had gotten strange. First, the man who called himself Bruce couldn't be found anywhere on Earth. He claimed to have amnesia. Second, this amnesiac man was far too capable. He could use martial arts to beat back monsters and carry out an entire investigation, from searching for evidence to taking statements. He was practically a jack-of-all-trades, except that he could blow up the kitchen when he cooked. Sometimes Zero even thought that if the Defense Force had more advanced equipment, Bruce could handle the monsters without his help. As the two continued working together, Zero gradually learned about Bruce's past, and the kindhearted Ultra Warrior immediately decided to help him. Zero: Look, you need to transmigrate from one world to another to find your family and friends, and I can freely travel between worlds. We're the perfect partners. After learning that Zero's age, converted into human years, still made him a child, Bruce became exceptionally tolerant of him. Unable to resist without resorting to force, Bruce could only accept the arrangement. - As their journey continued, Bruce gradually found the people who mattered to him. However, they might have a little trouble getting along with Zero. Dick: Bruce's partner? Are you the new Robin? Jason: Bruce actually lets you use his body to pilot a fighter jet?! Tim: The real question is whether Bruce actually lets him stay in his body. That's Batman! Damian: Damn it, you despicable alien! You stole the Robin position while I was gone! Alfred: Master Bruce, I'm delighted to see you again. But I never thought that while I was away, you'd end up having a minor look after your meals. Clark: Wasn't Batman's best partner me? Does anyone remember that we're the world's greatest team? Hal: Wow, the old Bat turned into an alien with rabbit ears. What kind of dream is this? Diana: Well... Batman, you do remember that this child's father is still around, so you can't adopt him, right? Bruce: ... P.S.: ※ Important: No pairing. ※ Bruce has a lot of personal headcanons in this story. OOC warning. ※ The two protagonists are from DC and Ultraman, respectively, and both are among the strongest in their worlds. Peak intelligence + peak strength = maxed-out from the start warning. ※ Each arc takes place in a different world, and the main plot is finding people. Worlds currently planned include Detective Conan, Blazar, Justice Lords, Demon Slayer, Bungo Stray Dogs, and Jujutsu Kaisen. Others are under consideration. The main draw is the crossover, and things may change later. Premise: Starting over isn't easy, but sometimes it has to be done