Yama No Hime ⇒

The most accurate and natural rendering of in solid text (without spaces or capitalization changes) is:

However, if you need to preserve the original romanized Japanese word boundaries while using solid text (i.e., no spaces but clear reading), the standard way is: yama no hime

If the context is a name or title, it is often written as one word in English transliteration: The most accurate and natural rendering of in

Meaning: Mountain Princess / Princess of the Mountains no spaces but clear reading)