Uke and seme are childhood friends who became sex friends and uke genuinely loves the seme, but the seme only sees him as a sex friend. Therefore, he continues to date women while sleeping with the uke and the uke knows this and is somewhat alright with it. This story is literally just about the seme realizing that he loves the uke, but it's so bad. He's like "I can sleep with other women and treat you like the second option, but the second you (uke) sleep with another guy, I don't like that". The uke is just really dumb and stupidly in love with the seme. Love really blinded him.
Happy Ending Kuso Kurae