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um is it this one perhaps? http://www.mangago.zone/read-manga/when_the_yakuza_falls_inlove/
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From what I remember is the they had a rough time being together (i think there relationship was a bit toxic) since the seme is a yakuza and in order to not make the uke sad cuz the seme had to get a wife he gifted the uke with a beautiful yukata:kimono the ones that the wife would wear and the members of the group started calling the uke sister or anne something like that. That’s the only thing I remember about them.
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http://www.mangago.zone/read-manga/heart_strings/ kind of similar
I’m looking for this bl it’s a yakuza one. I don’t quite remember it well but the yakuza gave his lover a kimono/yukata and the group started calling him sister. That’s all I remember from it. If anyone knows what I’m taking about please let me know !