Chapter 15 is expected to come out sometime this week, as it’s almost done.
So here’s the omake/bonus manga to hold you over until then.
FYI: Chapter 15 is the last chapter of volume 3 (before this omake).
Volume 4 hasn’t even been announced yet as of writing this.
I’ll try using the publicly available web raws until it comes out who knows when.
––Harry
DL: Here
Read Online: Here