We Swore to Meet in the Next Life and That's When Things Got Weird! Vol. 3
Long ago, Princess Yuko and her knight, Harold, fell deeply in love, but their social stations kept them apart. So they swore that in the next life, they'd be together. Now reborn in the modern world, Yuko has been searching for Harold for nearly forty years. Just as she's on the verge of giving up, she finds him, only to discover... he's still in high school?!