For a thousand years, Logan Bale has wandered the world, bound by one unbreakable rule: he never betrays a promise. When his dying disciple entrusts him with a final request—to safeguard his family for three years—Logan accepts without hesitation.

To keep that promise, Logan marries his disciple's granddaughter and becomes part of her household. But rather than welcoming him, her family treats him with ridicule, disrespect, and constant humiliation.

Logan refuses to retaliate or reveal who he truly is. He quietly bears every insult, determined to see his vow through to the very end.

All the while, he keeps a promise to himself as well: once the three years are fulfilled, he will leave their lives behind forever.