The verbal promise was kept.

As the second son of an earl's house, I was shouldering almost all of my older brother's paperwork and administrative duties. Holding close to my heart the words of a girl I met in my childhood: "I'll come pick you up, so do your best until then." One day, a proposal came to me—to marry into another family. ※This is a fluffy and loosely-defined world setting. ※This is also posted on Kakuyomu.