Unable to Survive Without Sex With an N.P.C. Demon After Reincarnation

"You should thank god that I'm your first." If he licks and sucks my clit and inside so much... My magic power will spill out! This demon... He's too good at sex even though he's just an N.P.C. character! Mia, who died from overworking, is reincarnated as the saintess heroine in a "bad-ending-riddled R-18 Otome game". If she doesn't do anything, she will enter the demon brothers' hard sex route and die again... So, Mia decides to use the heroine's vast magical power to raise the youngest of the demon brothers, Caius, as a bodyguard! However, the only way to transfer magic power... is through extremely pleasurable sex! In all kinds of places and positions, the demonic piston doesn't stop no matter how much she cums! Caius, who is trying to overtake his older brothers, devours Mia's body with his bottomless vigor... The game events trigger one after another along with the appearances of the demon brothers. What is the fate of Mia who only wants peace and quiet?