Last Boss, Yametemita: Shujinkou ni Taosareta Furi Shite Jiyuu ni Ikitemita

Game strategies and bursting with cheats: a second life! The strongest boss in the history of RPGs takes the world by storm! One day, the Demon Lord Menas is attacked by the empress of the Noahic Empire and her Revolutionary Empire. In the face of a beautiful blonde girl, Alex, a mysterious sense of deja vu washes over him... This looks just like the prologue of the game "Resis-Noah" in my dreams! After realizing that he is the final boss of this world, he decides to fake his death so he can enjoy a new life. With his cheats in hand, the new dark hero strives for a life of freedom!!

(Source: Square Enix, translated)