From ancestors to descendants, the Stone of Life was passed on for generations and kept underneath in what is called the Gate of Life and Death, a crater over thirty thousand feet in depth to which no one has ever entered, even the guardians themselves for its danger; those who tried are said to never return home.
A guardian of the spirit world, Kohinoor, was sent off on a mission to summon the man who can save them and bestow his spirit the Gift of Life, a second chance into the spirit realm to enter the Gate of Life and Death and compel his soul eternal rest.
Kohinoor separated from his group and chose to go to Tokisebu, as the modern society was all but foreign to them and only considered the spirit of Mizore Hidero, but fell in love with a woman whom he did not know was Mizore's daughter. He promised her a gift from the realm but asked to keep everything a secret, even more so from what was to be their firstborn child for the safety of what remains in Babylon.
Mitsuha, a beautiful, sweet, and caring woman kept her promise until then. Sagiri will always ask who her father was or what he looked like, but Mitsuha will always come up with stories on how her father was a soldier who bravely fought for his country, even showing her photos of him carrying her as a baby.