Kanamori-San, The Widowed Elf

Kanamori-San, The Widowed Elf summary:

When he consoles Mrs. Kanamori, a beautiful elf whose husband has passed away, by saying "I'll marry you myself," he is taken in and becomes her fiance...? A sweet and precious pure love comedy between a clumsy Yankee boy and the slightly natural Kanamori-san, 500 years apart.