submarine started it all (but doesn't have much to do with ibuki's family except the tiniest "strained back" grandpa hint), supervillain mentions quite a bit about okinawa, and then stella maris delves pretty deep into it! i hope you enjoy reading, it's an intriguing storyline!!

fun fact there's even a new okinawan restaurant near ES now, this was revealed in fine's climax event lol not sure if it's based on the exact same restaurant as ibuki's grandpa BUT it does use the same background as that restaurant! (on that note, fine climax event is a bonus story to read since it's related to stella maris)