I swear to God, I tried to find the Mayonaka no Door single, but couldn't find it anywhere on the Internet. I took this file from Yifei's japanese album All My Words (I looked extensively for this album on the Internet as well, both in japanese and chinese.)

Well, it might not be straight from the single, nor have the B-side, but it's still a high quality version. The album and single versions are THE SAME, so don't worry about any differences.

Download (MEGA) (https://mega.nz/#!1HBHlaQJ!9kIlkWOJtuCC_7lkABzH7igT35bMml_RX-VbxAVyU9o)

If you want to download the All My Words album: https://mega.nz/#!IHQ1QBqK!Xpnh5JDgyd32tmLtW_qEdaapS7GZMQNfGKgnjNR_YRA

Thanks!