Well, I managed to think about many things in my town, so I just came with an explanation related to Danganronpa.
*Kiki was an Ultimate. Ultimate Pianist, to be frank. She had an ebony piano before, but she sold it in ReTail. So... I started to think she was part of the Ultimate Despair and helped control people's minds with her music (if DR3 has a Brainwashing anime I can have a Brainwashing Song), but she regrets her actions. Before she sells the items she thinks it's better to teach a few lessons to my mayor, so he can actually inspire hope with his knowledge and talent.
*The mayor came to Saishuu to inspire hope in a new town, after his previous home in Wild World, Sasatio, fell into Despair. This time, he tries to be a friend of everybody, but he fears the idea of losing them, so at first he finds himself unable to trust anyone. But with Bud's help, he starts trusting the villagers of Saishuu, and starts transforming the town into a place to inspire hope and cure people's pain. He's the Ultimate Hope. Also, he's currently dating Bud.
*Isabelle knows everything that happened to Sasatio, so she tries to comfort the mayor by pep talks every time he goes inside of the Town Hall. She's the Ultimate Secretary, and that's why she doesn't take the role of the mayor. She thinks it's not her duty and happily hands the role to Kazuo.
*Alfonso came from Song in search of hope, too. This is why he bonds easily with Kazuo, they're able to relate in many things relating to their lives. He's the Ultimate Fisher. Also, he's Henry's boyfriend, but decides to keep his relationship private. The mayor knows anyways, but he still waits for the time Alfonso decides to tell him.
*Bud's the Ultimate Painter. Despite his appearance, he's actually excellent when it comes to tell if a painting is fake or not. He has a crush on Kazuo, due to his constant training with him. He tries to help Kiki with her broken friendship (Peaches and her had an argument. She regrets telling Peaches off).
*Henry is the Ultimate Fashionista. He knows everything about clothes, and gives his neighbors some clothes as housewarming gifts. He subtly tells Kazuo about his "close friendship" with Alfonso, expecting to see an angry reaction, but instead, he finds support and encouragement. And now he gets help from Kazuo whenever he wants to give him an undercover gift. He also helps Peaches and Kiki's friendship, but more on the other's side. He was waiting for a change in Saishuu, seeing as the town was completely empty, aside from Hamphrey and Wendy, three of the five originals.
*Wendy is the Ultimate Chef. She's Walt and Bud's best friend, so whenever she can she likes to give them fruity milkshakes and smoothies. She's asexual, so she's not interested in sexual relationships. As of now, she likes being Claudia's girlfriend, who's the most understanding of her. She's a friend of Midge, who recently moved out.
*Walt is the Ultimate Interior Designer, at first he's standoffish, but deep inside he cares a lot about the rest of the cast. He's close to Kazuo and Kiyotaka. Other than that, Groucho and Kiki know very little from him.
And I'm considering ending this here, since I'm dry on ideas lol. but feel free to comment on this. It was rather fun to give my town some sort of backstory.