As of now, Uta is indeed alive. The story hasn't depicted anything otherwise. Maybe there'll be changes in the future, but for now, Uta's part in the manga continues with them being alive.
Another plot could be that they are in a music competition. Yuzuki Yukari is known for her traditional - inspired music, while IA has a more futuristic sound. As the competition progresses, they start to borrow elements from each other's styles, which not only makes their music better but also makes them realize how much they can learn from one another.
It could be a story where Yuzuki Yukari and IA meet in a virtual music world. They might start as rivals, competing to create the best music. Then, as they learn more about each other's styles and stories, they become friends and collaborate on a masterpiece that takes the virtual music scene by storm.
I'm sorry, I'm not really familiar with the specific 'Sleepless Cinderella Party Yuzuki' story. It might be a relatively niche or new concept that I haven't come across yet.
Their relationship could start with Uta being initially distrustful of Luffy. After all, Luffy is a pirate and Uta has her own ideas about pirates. But as she sees Luffy's pure heart and his determination to protect his friends and pursue his dreams, she starts to warm up to him. They might then become friends who share their different stories and experiences.
" Uta's Dream " and " One Piece Uta, The World's Songstress " were two novels recommended for playing Uta. Both novels had stories and character settings about Uta.