Today I decided to give Blood Blockade Battlefront another shot (the aesthethic of Leo's eyes never left me, no matter how much the anime overwhelmed me), and apparently I was so overwhelmed that its ED completely left my "active" memory.
I remember playing Sugar Song & Bitter Step for the first time in bandori and the song flowing out of my hands as if I knew it, but I had no idea how or from where.... today that mystery has been solved. That was nice. It's a great song. To know it didn't felt familiar because of some other song, but because it was familiar soothes a worry in me, haha.
(Yes, I tend to not remember what song tied in with which show/game if the title doesn't ring a bell. Sue me.)