How about checking Merry's mole list, you may recall it after seeing cover & summary..
http://www.mangago.zone/home/mangalist/25637/
than you .. but too bad it wasn't there :((
Do you remember any other stories from that manga?
too bad but I dont as this story was the one that left the impression.
sound like this one
http://www.mangago.zone/read-manga/yoiko_no_sumu_machi/
first story
thank u thats it... i new that it had similar art with aitsu to ore, but couldnt find it with its cover, totally overlooked it.
I think there are few stories under one title.. first story is about friends becoming lovers, one is trait and another gay who is in love with someone another. he has a mole on ass or somewhere around there.. straight one sees it when he has sex with him first time as comfort... I'm sorry for sloppy writing.
oh and gay one is harassed in toilet in next chapter