[Seitsuki]

That would be rather difficult, as there are usually multiple readings for romaji.

The only method I know of sorry is to type in JP the romaji of the word you're looking for then scroll through the possibilities, maybe using google/dictionaries if you're still unsure. I believe any online resource would operate on a similar basis (laying out all the possible spellings).

Btw what you're looking for is 妖狐.