Honmono no Seijo ja Nai to Bareta no ni Outei Denka ni Semarareteimasu

Selma is a saint who doesn't have any sort of holy or divine power. Because there's no need to make that fact known, she keeps it a secret from those around her. But there is one man who is suspicious of her: Theophilus, the royal prince. He joins the church as a believer, and begins casting doubt on Selma through any means possible. Then, through a set of pressing circumstances, it's finally revealed to him that she's a fraud! And yet he tells her, "I want to be the only one who understands you," and begins trying to get even closer to her! Source: KADOKAWA