Kasai

Kasai can represent Japanese surnames written with several different kanji, as well as an unrelated Japanese word for a damaging fire. Those are not interchangeable: a shared pronunciation does not mean that every person called Kasai has a name meaning fire. The original written characters are important when a Japanese surname connection is intended.

Kasai is also the name of a Central African river, providing a separate geographic association. In modern American use, a family may be choosing the sound, a surname, or that place name. Identifying which connection matters makes the story more accurate than applying one Japanese dictionary gloss to all uses of the Latin-letter form.