Zense de Aishita Hime ga Tensei shitara Ojisan deshita

Once upon a time, a princess and knight loved each other very much but they never tied the knot. The two vowed to find each other in their next lives. Bartholomew the knight has been reborn as a high school student named Haruto and has spent his whole life searching for Princess Claudia. But when he finally finds his princess, she's a fifty-something high school vice principal and a father! But this knight loves his princess in any form.

On the other hand, "Claudia" is self-conscious about now being a middle aged man with a dad bod and how others might perceive a relationship with a younger man. The princess just isn't ready to accept Bartholomew's feelings yet. Can the young knight win over his fated love?

(Source: Seven Seas Entertainment)