Demon God, Don’t Turn Evil

[A seemingly aloof little goddess with both brains and beauty VS a cold, proud great demon who hides a dark side] As the last god in the world, what should she do? Obviously, eat and sleep. Ahem... protect all living beings. And so the goddess, entrusted with a heavy responsibility, descended to the mortal world to vanquish demons... When they first met, he was still a tiny bundle, while she was a little glass fairy only he could see. To keep the little bundle from turning into a demon, the goddess told the biggest lie of her divine life, which had already lasted ten thousand years... When they met again, the little bundle had grown up into a devastatingly handsome young man. Every time she saw him, her heart raced. But who was she? A mighty goddess! How could she be swayed by good looks? Besides, she had lied to him back then. If he found out about her secret identity, she'd be in serious trouble... Later, her secret identity was exposed after all, and she lost her heart to that scheming great demon... The little goddess, having failed her mission: “Waaah, it's all my fault for being useless. I couldn't complete the mission or protect my heart.” The great demon, with a cheat up his sleeve: “There's no way I'm losing. Not in this lifetime. I make the rules of the game, and if I really do lose, we'll just start over.”