Song: Your Heart and I Becoming One
Composer: Masa [まさ]
Singers: Miku Hatsune and Gumi Megpoid
Subbing/Translation: Despair Media. Youtube channel is https://www.youtube.com/user/Mock1ngjay
Side Note: The song "The Fox's Wedding" and "Your Heart and I becoming One" is part of a story made by Masa [ まさ]. It's called the Onibi series.