Musubi-no-Kami's flower refers to the Sakura Blossoms, in Japan, or otherwise known as Cherry Blossoms, are said to be given to unexpecting women once a year by the Japanese God of Love, Musubi-no-Kami to grant them prosperity and love. The song, to me, plays on that aspect but in a more dark and gloomy way. Like, love can conquer all, but love itself can be a war.