they go from close to strained to close
mob tells ritsu a lot about whats going on with her, ritsu also gave her spare keys to his shared apartment and sometimes she crashes there when shes overwhelmed (which is where the straining part happens) mobs kinda jealous of ritsu seemingly perfect life esp when everything going on with them is a wreck and is unstable with mob. but regardless in the end they're still always gonna reconcile in some way since they're siblings <3