Itoshigo yo by RURUTIA, for sure. Both the song and the PV are unsettling, but especially the ballad version.
https://www.youtube.com/watch?v=y61Ljta2T-o
Excerpt from the lyrics:
You don’t have to worry about her anymore
Even if she does come and try to dig her claws into you and take you away again
I’ll beat her to death with these hands
Don’t resist, entrust your everything to me
Only I can revive you
I’ll shred your wings
So you don’t fly away somewhere