For me it was just like relationship between power and weapon....where power is Miyuki who only believes,care,love and has affection for her brother...same goes Tatsuya...who clearly thinks,protect,enjoys time, and gets calm by Miyuki only.He has no one else in this world rather than Miyuki and vice versa where miyuki has same thought....
Tatsuya is cool ,emotionless guy who doesnt give a s*** for anyone or anybody, except Miyuki.He cant be defeated, he cant be conquered by love of any other girl.If he sees Miyuki in trouble then whole world gets f***** up.He goes up on rampage and can only be calmed down by MIYUKI....
Overall : As story i like it a lot but relationships was quite weird but at the end it was good as they dont even kissed or got into some other incest.All the characters were awesome and played a important role in this story....
It reminded me of ATTACK ON TITAN:
Tatsuya = Levi(Hero Cant be defeated)+Eren(his goal to kill and defeat all titans for his mother and ones he loved)
Erika(her fighting style and aggressive beauty)+Miyuki(affection towards protagonist-brother) = Mikasa(so called brother eren)
I`ve just watched anime only but is it true that in novel its mentioned that Aunt Maya tell Tatsuya that she is not her sister and then they get engaged,also miyuki is now new heir..and they both accept this but because tatsuya emotionless character its hard for him to focus on love but he is working on it...
