So the funny thing in the title is that 4 in japanese could be pronounced as "shi" as in ichi, ni, san, shi (one two three four) and the initial of 1 (ichi) is "i" and that makes 04R1 a pun for "Oshiri" (the 0 is just O) which means ass
Checking the raws shows that yes, there's only one volume and it ends with chapter 19.
Souryu is probably too busy doing his other manga to continue this.