How are Dark Souls and King’s Field connected?
Nobody at FromSoftware calls Dark Souls a King’s Field game, and Miyazaki actively resisted connecting Demon’s Souls to the older series. The documents still describe the relationship in the same words at every step: spiritual successor. Demon’s Souls was called a spiritual successor to King’s Field; Dark Souls, blocked from being a literal Demon’s sequel by Sony’s ownership of that property, became the spiritual successor to Demon’s Souls in turn.
What passes down the line is not plot. Miyazaki himself cited King’s Field’s dark tone and high difficulty as Demon’s Souls’ main inspirations, and King’s Field’s reception history reads like a review of a Souls game fifteen years early: praised for complex labyrinths, large seamless worlds, and stories with epic scope in a limited space.