Why Is There an Ultraman in My Quintessential Quintuplets Youth?

To defeat a powerful enemy, the Ultra Brothers sacrificed themselves. Their souls fell to Earth and encountered the Nakano quintuplets, who had lost consciousness in a crisis. From then on, the souls of the Ultraman fell into slumber.

To awaken the Ultra Warriors, Seven's son Zero transformed into an ordinary high school student and went to live among the five sisters, hoping to rouse the sleeping souls of the Ultraman. And so the story begins.

"Ichika, Nino, Miku, Yotsuba, Itsuki, which one of you..."

"...is my dad?!"