New chapters come every two months with longer a gap in between volumes. We're still in the middle of volume 5 with the last ch released in early February. So next chapter should be out between April 5-10 depending on how fast it gets translated.
I know this because I was also getting my hopes up and then dashed cuz extrasss ;_;
In the meantime, I read Acid Town by Kyuugo. It also takes place in the yakuza world and helps with my Saezuru cravings.
*cries* ugh...nyooo....*sniff* *sniff* acid town...? ima read that to fill this void in my heart...gracias *sniff*
Me: *sees update* WOO! OH MY GOSH IT'S TIME!!!
*reads chapter*
Me: ....ugh...it's cute and sweet and ugh but also ugh...new chapter no...ugh...