Sounds like this one, but I'm not sure:
http://www.mangago.me/read-manga/doutei_hitsuji_to_abazure_ookami/
In this manga there is a one shot story inside with a similar plot.
http://www.mangago.me/read-manga/kouun_no_rihatsushi/
Ohh the name is on the tip of my tongue. Are you talking about the yaoi that's about a band the singer were girlish clothes and is in love with a childhood friend that has a little girl. The bassist goes to a convince store and buys the same thing every night to see the clerk and the drummer is the one who sleeps with a guy in a public restroom because he is addicted to sex.
You're right, I remember now. It's ch.6 (3rd story).
i search a yaoi one shot manga...the guy(uke) black hair looks like a punk and the seme ist a normally man...
one day the uke wanted to have sex and the man was there they have sex on a toilet i mean ...somthink like that