It Turns Out That They Are the Protagonists

I, The Founder Of The Shi Dao Sect, Fought Against The Heavenly Dao With All My Might, Only To Die In The End And Be Reborn A Second Time As A Mere Cannon-fodder Playboy. Watching Those Girls, Who Are Destined To Ends Up With Protagonist… My Heart Ached… Huh? They Said They Like Me?!… Fine! Then Let’s Joyfully Cultivate Together ~ And Defeat Those Protagonists… What? You Said? Wait, They Were The Real Protagonists From The Start?