"So is everything ready?"
"Yeah, you'll have one year, maybe two, to convert enough magical girls, plus enough familiars to keep them coordinated, and some few guardian beasts to serves as meat shields."
"WHAT?! That's not nearly long enough to get enough together the old fashioned way!"
"Yeah, well, I'm not exactly making the invasion schedule, if my bosses KNEW I was spilling the beans I'd be dead by now. But I am gonna provide your new-girls with some on the job live-fire training, since I'm the one whose job it is to send out the forerunner Hunters and Gatherers monsters, I'll keep them as piecemeal as I can without rising suspicion."
"But humans are the only sapients LEFT in this world. Do you realize what you're asking me to do?!"
"Yeah, well, it's either that... or you can sit back, and tell humans to prepare their laser beams, bullets, and nuclear warheads for creatures whose physical forms are only projections from the spiritual plane that normal human senses and equipment can't even detect! It's not my fault YOUR bosses' 'let humans decide their own fate' policy let them like chicks against chickenhawks."
"Not this again Imina."
"Doesn't change the fact Iris . . . Just fair warning, this invasion is gonna be BIG... so I suggest you recruit as many as you can."
Imina vanished through a dark portal.
Iris sighed. "Okay, let's do this." Anyone transformed into a guardian beast or familiar, would see such as their reason for living, and would protect/guide their magical girl(s) to the death regardless of their lives before. Same went for any who became magical girls, 'love and justice' being why they drew breath. Well, best get started.
One the first ones were transformed, they'd instinctively and unconsciously be drawn to others who fit the profile, and recruit more themselves. On the plus side, the thing that would make human sitting ducks for the Dark Side meant humans would be obvious, or see what they saw as normal (and maybe some reality retroaction... ).
Three friends were checking out their new iPad, when an advertisement popped up.
'Would You Like To Be A Magical Girl? A familiar? And a Guardian Beast? And risk your lives to protect the world? At the cost of all else? Never to get back what you've lost? Yes/No?' (Several pages of Disclaimers followed, including not liable for changes to reality, dismemberment fighting demons from hell/tartarus/neither world/etc ).
The three friends looked at each other, laughed, and clicked yes.