Hmm... from the app skimming and poking a bit at wikis, if we don't go for Shinigami = Death (where it's like rebirth of the self too), I think Temperance and Hierophant would also be nice fits for Rukia! Because it has adaptability to different situations and calmness for the former, and Hierophant has the stuff about upholding the old but also taking in the new. That paragraph about her willingness to learn about human culture was so cute to read...

And aw oh no that sounds so cute. Minato's not used to being taken care of at all but that'll probably just make it even more fun to thread. ;o;