Onimotsu to Yobareta Tensei Hime wa, Shoukan Yuusha ni Koi wo Shite Seijo ni Narimashita

In a kingdom where magical power is equal to the power to rule, Reya was reborn as a princess with no magic, and is forced to live her life in the shadows. However, when it was discovered that she has the same purifying power as a legendary saint, she is recruited to help the powerful hero, Kazuya, in the neighboring empire. Reya is happy to finally be of use to others, but the hero seems strangely cold and distant towards Reya...? This is a story between an unappreciated saint and the strongest hero, working together to find love and save the world.

(Source: Ura Sunday, translated)