Bio + harem

Aside from the Nemesis project there was another project called Kizunamio. this project was meant to create artificial spirits. They hope to surpass the original spirit and sell them to make profit. So they went out captured about 10 different spirits and start experimenting on to to see how they worked and how their powers worked they then grab the failures from the Nemesis project and rework them into this project out of the 15 only five survived and were considered success developing angels and Demon Kings of their own. They have officially surpassed at least normal spirits able to wield both angels and Demon Kings but around 17 years later after their success one of the spirits went rogue killing the other four before disappearing.