Responses
The first chapter of this series that is chapter 4 was first in a compilation of BL manga named Nikutaiha, so that is why they added the chapter in this later I think, to complete the history when the volumen was ready with all the chapters published maybe
thanks for that info, makes more sense!
is it just me or doesn't it feel like chapter 4 should be chapter 1?? since even sensei it curious what will happen to Ushio, I'm going to quietly hope for a spin-off (*・～・*)