I'm scrolling thru the comments and ppl seem to hate ruby, but she's childish for a reason. She never had any social interactions that were normal for her age (chatting with friends, crushing over boys in her class that were her age, etc). She developed a dependency/obsession on Ai as a coping mechanism and attached herself to the only person that paid her any attention when she was alive, her doctor. She living a horribly short, uneventful and lonely life, and I think she honestly doesn't care abt Aqua technically being her brother bc they were full àss ppl with complete personalities before being reincarnated. She's acting spoiled and bratty because she's literally a child that never got to experience adulthood--everyone around her has always treated her like a child. Aqua is like an adult in his 40s by now, he treats his "sister" more like a coddled child. He feeds this unhealthy dependency on him from his "sister" because he understands this is the continued life of a very unhappy and lonely little girl. The incest is crazy gross to read regardless, but this is all to characterize ruby's actions/behavior in context.