Unfortunately, the original song is impossible to find. This is a cover with Hatsune Miku. The song is from the album “Yuunagi Loop”:
We have featured Niyaz before here, here, here, here, here, here and here. This is from their album “Niyaz”:
We have featured Kunihiko Ryou before in this blog here, here and here. This is from the “Eikoku Monogatari Emma” soundtrack.