The Epic Beginning
When Tadashi had survived the fire he discovered something important: His mutation made it so he could heal ultra-fast. He could also control fire to the point that he could make himself combust into flames. He wasn't sure why healing came with this power until he followed it to the logical conclusion. If he can burst into flames, the first time he did that, he would die. But since he could heal, he had no ill effects.
But this story isn't about what/how Tadashi uses his powers. This story is about how Tadashi and Hiro are immortal. How they cannot die and how they decided to reboot the Big Hero Six team. Tadashi was visiting his daughter, Jamie, at her house with his own grandkids. Tadashi didn't look anywhere close to 30 years old, much less 50. But it didn't deny the fact that he had kids and grandkids. He was actually supposed to be in his 80s. Gogo had died at 65 years old with a severe cancer.
Hiro was 73 years old and Honey Lemon was in a nursing home. She has alzheimer's disease and Hiro was visiting with her. Once Hiro was done visiting with his wife he went to see Tadashi. Tadashi was waiting at Hiro's house, sitting on the front step. Hiro sat down next to his brother and looked at the ground.
"How's Honey?" Tadashi asked, picking a piece of grass and crocheting it carefully into a chain. He looked back over at his brother with worry.
"She remembered me today," Hiro offered as he stood up, turning to let them both in to his house, "Genesis visited her mom today. I was happy to see that. She also asked about the Big Hero Six team. I told her we disbanded."
"What did she think about that?" Tadashi asked as he stood up and followed his brother inside.
"She wasn't very pleased with the decision..." Hiro sat down at one of his chairs and looked at Tadashi, "So...Do you think we should reboot? I mean, we're here. We could redo Big Hero Six. We would just need members."
Tadashi slowly looked at Hiro and contemplated if he had gone insane, "Say again?"
"Rebooting. Big Hero Six. We could do it," Hiro summarized what he said before and watched as Tadashi got a thoughtful expression. He waited until his brother shrugged.
"Where would we get the members? Our kids have kids," Tadashi pointed out and asked in the same moment. Now it was Hiro's turn to think.
Hiro finally just shrugged and said, "We could keep an eye out for mutants. I know of a couple. Anastasia. Remember her? She is a fairy godmother in training."
"What will she do to the criminals? Make their dreams come true?" This was asked extremely sarcastically by Tadashi.
Hiro gave him the look of death and said, "She is a start. She might know some mutants."