Actually really curious about Bell's right hand-related lore if you don't mind sharing? If you do you can ignore the ask 🫂
THANK YOU FOR ASKING ABOUT MY INSERT
Bell is a similar situation to the remnants, two members of Bell's class were poking their noses in Junko's business and were suspicious of her, so Junko pretty much broke Bell (who was already infatuated with her) and sent her off to stop her own friends from getting in the way of Junko's plans.
Bell masterminds a killing game of her own class in Junko's honor sort of? Kind of a "I wanna be you" thing, it's hosted in the decaying remnants of Hope's Peak which is now crumbling apart, and once the survivors get out, Bell is left in the rubble (presumed dead) where she finds Junko's corpse, and takes her right hand since it was some of the only bits left of her that the remnants left behind, sort of as her punishment for herself for not only losing but hosting the killing game to begin with.
Yada yada, she does end up in Towa and meets Servant, she cares for the WOH with him until future foundation rounds up the remnants and they get put in the NWP along with Bell. Bell does survive the nwp killing game, waking up long before Nagito and waits for him pretty much every day.
I've been developing this for like a year some details between could change lol