ayirip's manga / #slutty uke(35)

I can't understand Sendou's thinking process really. His character is a mystery to me, but I've always have problem understanding slutty uke/seme. Lol. His insecurity is what I dislike about his character the most. I don't even understand why someone would fight over him. Is it because he was so good in bed? I can't seem to like any character in this manga except Hotta and Akiyoshi.