it's a manga where two brothers are taken in by a wealthy family... the younger brother is the uke and constantly screwed by a member of that wealthy family... somewhere along the story he caught his brother, who he really looks up to, having an affair with another member of the rich family... in a kimono.
That one with a zashikiwarashi uke and a salaryman(?) seme. I remember that it's a oneshot in a series?? I forgot the title orz pls help
Found it. It was Kiss shite yowamushi kun, ch. 3!