Before the start of the series, Yuuno lived in Mid-childa, a magical world, as an archaeologist. He had no parents, so was raised by his entire tribe, the Scrya, from which he took his surname. He also obtained or created the intelligent device Raising Heart around this time, but his talents lay as a support mage, and so his attack abilities were low and he never made the device into a weapon.

Yuuno first appears running from a gigantic monster in the woods and attempting to seal the Jewel Seed inside it with Raising Heart. He fails, letting the monster get away, and collapses wounded on the ground. Yuuno uses his remaining power to call out to the nearest magic user and turns into a ferret. His call was heard in Nanoha Takamachi's dream, and later that day, she found the ferret in the woods and took him to the veterinary hospital. He quickly recovered, taking a liking to Nanoha and recognizing her as a possessor of the magical aptitude, a rarity on Earth. Later that night, he calls out to Nanoha again and she leaves the house and finds the Yuuno-ferret cornered by the same monster. He entrusts her with his weapon, Raising Heart, and seeing her raw power when she activated it, deduces that she can create magical armor and turn Raising Heart into a weapon of her design. She does so and begins her journey to seal away Jewel Seeds.