Whenever the Ōtsutsuki Clan planted a God Tree on a new planet, they had to sacrifice a lower-ranking member of their clan to nourish it. Ōtsutsuki Kaguya was one such offering, destined to be sacrificed.
In ancient times, Ōtsutsuki Isshiki and his guardian, Ōtsutsuki Kaguya, were sent to Earth to plant a God Tree. To successfully cultivate the Ten-Tails into a God Tree and have it bear a Chakra Fruit, Isshiki intended to sacrifice the lower-ranking Kaguya to the Ten-Tails as planned. He never expected Kaguya to ambush him, leaving him unable to fight and gravely wounded, on the brink of death. (Note: a successfully planted God Tree already existed on Earth.)
But the gap between their strength was so vast that Kaguya failed to kill Isshiki outright and let him escape. Still, she left him badly weakened, unable to stir up trouble for the time being. Eventually, Kaguya successfully ate the Chakra Fruit borne by the God Tree. Her strength soared, and she felt she could take Isshiki on, but he seemed to have vanished without a trace.
To prepare for the members of her clan who would come to Earth in the future, Kaguya made extensive preparations. White Zetsu was a product of her efforts to fight her own clan, but in the end, her two unfilial sons betrayed her and sealed her inside the moon.
Meanwhile, the gravely injured Isshiki was terribly weak after the Ten-Tails bit off more than half his body. As he lay dying, a bald monk named Jigen became his unlucky victim. Already half dead and utterly drained, Isshiki could only secretly use his secret technique, Sukunahikona, to shrink his entire body and slip into Jigen's ear, then use every last ounce of strength to mark Jigen with Kāma.
After marking Jigen with