Perhaps, breathing the air of the same time and space with the one you love, within arm's reach is the best interpretation of happiness.
Perhaps, what Immortal Dao gave up for Rukawa was not only his future, but also the whole world;
Perhaps, Rukawa gave up not only his whole heart, but also the whole world for the sake of immortality.
No oaths or commitments are needed, the tenderness between the fingers is enough.
Waiting for the Spring and Autumn Period, waiting for the fleeting years, and smiling together...