Raising Magical Girls, and Leave Them With Eternal Regret?!

“What’s the best way to defeat someone?” “Destroy beautiful things in front of them.” “What about a magical girl? Someone with the power to protect everything?” “That’s quite easy as well.” YouYu smiled and said. “When she’s still naive, becoming the most beautiful thing in her heart.” “And then…” “Die in front of her.” (Make her live with eternal regret!) After all, a “villain” is not within the protective range of the “heroes,” right? However… the actual situation seems to somewhat differ from YouYu’s expectations. Why, after his “death,” all these magical girls are now trying to imprison him?