sweet potato
Also called a camote, it is a type of tuber vegetable that isn't as starchy as the potato, but instead has a sweeter taste. Tends to be mislabeled as a yam, but they are from an entirely different botanical species. This is also known as a food that makes you gassy.
Popularly associated with Aki Minoriko because she wears a sweet potato-scented perfume, and has a spellcard named after them in Mountain of Faith.
Chiyoda of Kancolle fame is also pretty fond of them.