There's no ambiguity: in Hepburn, Konan is always "Ko-nan", you'd need to write it Kon'an if you wanted "Kon-an". Which is also unlikely in Japanese, unless yo

There's no ambiguity: in Hepburn, Konan is always "Ko-nan", you'd need to write it Kon'an if you wanted "Kon-an". Which is also unlikely in Japanese, unless you're writing about root vegetable safety 根案 or something. If anything, using stress marks would be worse, because Japanese is (slightly) tonal and accents are on rare occasion used to mark them: háshi vs hashí.