What is a Japanese word for soul sword or to say a soul is inside of a sword?

It would be much easier to answer this through direct speaking, but...

霊 刀

the first kanji above, means "soul, spirit"

the second kanji, means "sWord, katana, (specifically a single-edged sWord)"

the first kanji is pronounced "tama" and the second is "ken" or "tou" or "katana" depending on the specific use.

内 This kanji means "within, inside" and is pronounced, "nai"

so, with my limited knowledge,

霊内刀

would be "tamanaiken" or something similar.

I would be better able to name it with direct communication, as there is very minimal direct translation between such different languages.

If you are able, please include A more in-depth usage for your term to be created.