Board Thread:General Discussion/@comment-25372545-20141221171343/@comment-5553481-20141227193450

Chakra in Naruto is a mixture of physical and spiritual energies, so chakra users would be able to see spirits.

Ki/Chi in Dragon Ball is the "life force" of a person, theoretically speaking a person is made of both body and spirit/soul, hence the life force would be made of both as well, so ki/chi users would be able to see spirits.

I would assume most of characters that save the world in other mangas/animes would also be able to see spirits because of their power.