Onee-shota RPG: The Young Exorcist's Lewd Battle

Mamoru Ichinose, a boy who lost his parents in an accident at a young age and became an orphan, possesses an overwhelming talent for demon slaying that far surpasses that of ordinary people. Through a mutual acquaintance, he is taken in by the Amagasaki family.
He awkwardly forges a relationship with his new older sister, Noa Amagasaki, who dotes on him and calls him “Mamochi,” and Mamoru is finally beginning to find a peaceful and warm daily life.
However, that peace is brutally shattered overnight.
Awakening from the depths of a forgotten and crumbling seal is the succubus queen, Rosalia Violetta.
With her overwhelming magical power, Mamoru’s beloved town is instantly transformed.
Stolen from his memories as an exorcist, Mamoru is forced to become sexually intimate with his fake sister and to ejaculate with his fake mother.
He is then forced to attend the “Virginity Graduation Ceremony” at the completely altered school, where he surrenders his virginity, vitality, and all his demon-slaying abilities to Rosalia. Drowning in a sea of pleasure and with his mind rewritten, Mamoru has become nothing more than a pervert blindly in love with Rosalia, engaging in orgies with his classmates and descending further into lust…
Just then, tearing through space, appears Noa, the only one who has continued to resist the altered brainwashing!
“Mamochi, over here!!”
Regaining his senses at the sound of her voice, Mamoru escapes the situation, and despite his powerless body, he vows to fight back to protect his everyday life, his promises to his friends, and Noa, using the power bestowed upon him by the angel Pamela!