I like to think about little Ayato looking up to his Sister so much that he’s disappointed when his kagune comes out for the first time and it doesn’t look like Onee-chan’s. So he worked on controlling it enough that he could just make the single wing come out instead and he’s so proud to stand beside Touka- a matching pair.
Then when he left her behind…. gone are the days where he wanted to emulate his Big Sister. He starts flying on his own two wings (Edgelord Ayato even wears a shirt with two wings when he leaves)
And then when he becomes Rabbit, and reverts to using one wing again, that’s when the slow journey back to Touka begins *lies on floor*