Miki (u) like playing around with girls. One day he "help" Udou from girl who want to reach him by telling that girl "Udou is with me"
Then Miki ask him to go out for real. They become lover.
Miki already knew that Udou is a kind and gentle towards his girl
Miki ask Udou to have sex too coz they are lover after all.
But...... tough he is a playboy, when it comes with Udou, he become cuuuuuuuute
Gosan no Heart