>>2065496yes nana to karou is the prequal manga to black lable wich also as far as i know also goes by the name arashi.
my theory is that black lable/arashi pics up from nana to karou a year later, and the ending to nana to karou is semi decent, it personally left me wanting more wich i got a little bit of in black lable/arashi.
But again i mostly read it for the fapping material, but when it made me want to see what happend more than i wanted to fap to it, then you are telling a good story