Morphrey

Morphrey was a traveller and a human before she passed away and also the one that gave Koo a name before she went on a journey and died cuz of an accident. When she was a human, she yearned for freedom, admired how the birds soar in the sky, travelling to wherever they want. 

Due to her strong urge to see Koo one last time, she was given a chance to be reincarnated and with a pair of wings. Although several hundred years had passed before she was reunited with Koo... she was afraid things might've been different from the ways they used to be.