Chen Li knew Yang Guifei, and he knew her objective before the storyline had been altered.
Yang Guifei had modeled her Saint Graph after Tamamo-no-Mae's, so she could absorb monsters and recreate Familiars of the same type using just a single hair from her tail.
She had imitated the legend:—[The Nine-Tailed Fox created goblins and monsters from its tails, and all the goblins and monsters throughout Japan were born at that time.]
But Yang Guifei believed herself to be an existence that denied humanity, so her Familiars should not be existences from human history either.
Thus, she had transferred through the various Lostbelts, slaughtering monsters and absorbing them into her tail.
Each Lostbelt's information she absorbed added another tail.
Seven Lostbelts represented seven tails.
The eighth and ninth tails were the "Alien God" and Chaldea's Master, respectively.
That was how it should have been.
But because she had been born ahead of schedule, and because she knew the Seventh Singularity contained several Human Evils, had her appetite grown so large that she intended to absorb other "Beasts" to increase her number of tails?
That was truly courting death.
"So that's why you answered Chen Li's summons. Don't you know how terrifying Chen Li is?"
Rin Tohsaka truly admired Yang Guifei.
"I didn't know at first... but I know now. Master isn't terrifying at all! Beneath the extremely vicious exterior of his World Final Trial lies a profound love for the world! Just as Human Evil is Human Love!"
Yang Guifei had intended to answer like that, but when she felt Chen Li's cold gaze fall upon her, she decisively chose words that better reflected her instinct for self-preservation.
If betting on Chaldea's Master, having him and the many Human Evils mutually destroy one another, then sweeping the pot as the