Also you could say it's unrequited since Ruby holds a yellow rose [friendship] and Luther holds a blue rose [unrequited]. Ruby sees Luther as only a friend, but Luther loves her with her whole heart. <- This is entire subtextual only going off their art.

They both find solace in one another in wanting to just be seen as ordinary girls, as Maltese and Golden tigers are seen as rare or beautiful.

"Even among the tiger I'm a rare species, that's me, Maltese Tiger. As a miracle lion, everyone take care of me greatly but they never see my inside and there are times when it's painful for me... ... But, I met Ruby who has same situation with me, together we aiming to become ordinary girl while we also do our best." - Maltese Tiger [Luther]