Yuiji is from a well-to-do family that oversaw an airship trade vessel operation in Piltover. They had minimal influence over politics until Jayce introduced the Hexgates. They gained a ton of power and influence out of nowhere and Yuiji was dragged into the family business with more urgency than ever. Before, he was happy doing mundane inventory counts and maintenance checks on the airships. He detests the politics that he has been suddenly exposed to. He's begun running away from home at inopportune times and maybe wandering a little further than he should be.
Yamato was originally from Zaun, but his talent in Joltball found him recruited for a Piltovan league. (Idk, Joltball is soccer in Piltover, but imagine tech footwear and a more dimensional field with obstacles) He's constantly ostracized and isolated by his topsider teammates. He's persisting to bring back money for his folks, and he's just hoping to continue with the sport until he can afford to buy a house for his family in a more affordable neighborhood in Piltover and leave the sports league behind. He finds himself hanging out on rooftops and staring at the airships above for a sense of escape.
Hongou's family is a very influential family in the world of politics, but he has so many older siblings, that his role in the family hierarchy is fuzzy and unestablished. He often ditches family functions (without much flack) to attend concerts, art installations, and sports events. He's Yuiji's best friend and he's incredibly good at distracting Yuiji when the young scion is supposed to be conducting an airship inspection or drafting an important letter to a trading competitor.
A young Zaunite tinkerer who is apprenticing under a clockmaker. The business is actually doing fairly well since it has drawn a decent amount of customers from the topside. Growing up, she spent a lot of time with Yamato running through the fissures and climbing into abandoned buildings. She built his earliest sets of Joltcleats and more than a few of them short-circuited and starting sparking when they definitely weren't supposed to. Yamato still visits her to get his pocketwatch tuned up. Nacchan always asks Yamato to bring her back Piltovan pastries back when he visits.
A Joltball player in the same league as Yamato. He's from a well-off family of architects and Joltball is just a hobby for him. When he's not practicing, he's studying to become a politician. He hopes to get to a point where he can be a policymaker and write laws for the good of Piltover. His initial goal was to focus on housing laws, but meeting Yamato (the first Zaunite he's ever talked to) made him start to think things differently. After matches, he began hounding Yamato to take him to get coffee and get dinner. Yamato initially refused, feeling that he was getting targeted for being a trencher (he was), but eventually relented because Seki was so persistent. They eventually became good friends when they got past their first impressions of one another.
A young recruit in the enforcers. She got into the force through sheer display of skill, but her higherups still won't give her any major or dangerous assignments due to her age. She's usually plopped into checking tickets for cable cars and other public transport. Sometimes, she's monitoring security for trading goods. She's always terribly bored and upon meeting Hongou who would chat up a storm during her patrols, she became fast friends with her new source of entertainment. She would also soon befriend the young, drowsy-eyed scion who visited the airships for routine inspections.
His parents are Zaunite engineers who moved to Piltover before he was born. His whole life, they've tried to assimilate into Piltovan norms and did everything they could to raise Sakura as the model Piltovan citizen. He's exasperated with his parents' obsession with image, but he loves them otherwise and is happy to take up the family business. He's currently working with them to design Joltball fields and arenas. When Yamato joined the League, Sakura's parents were insistent that Sakura not interact with him, but when Sakura noticed how lonely he was, he couldn't help but approach him.
Originally from a Noxian family, Akiyama ran away/was banished (?) (the story changes depending on who you're talking to) to Piltover because the tech and gadgets would be more suitable to a "soft" person like him. Being estranged from his family, Akiyama was happy to start a new life in Piltover and managed to score well enough in the exams to enroll in an engineering university. When he meets a sour-faced kid who barely goes to class and leaves early one day because he "has a job with his parents", Akiyama ditches class too to see what's going on.