The Angelic PE Treatment Clinic

The protagonist has a rather embarrassing problem: because he has premature ejaculation and is a total masochist, he loses without fail to every monster girl he encounters in dungeons. But one day, he happens to stumble upon a sign that reads, "The Angel Clinic: Specialist in Premature Ejaculation Treatment"... Spoiler Inside, he meets Sera, a poker-faced nurse who claims to be a literal angel. To his surprise, the treatment she proposes involves him trying to resist her seductions in order to get used to erotic situations. Bewildered but desperate, he agrees to the therapy. As expected, he is no match for Sera's alluring charms and ends up thoroughly humiliated. However, despite her expressionless facade, the words that come out of her mouth are full of affection: "You're so cute," and "I like you..."