Time paradoxes are terrifying things.
As a Time Dragon, as a Prophet Mage, Fang Zheng had always been deeply concerned about this issue. At present, the time paradox that Kurumi was facing was similarly terrifying.
Kurumi wanted to kill Mio Suginomiya before she created any spirits, but Fang Zheng doubted she had any chance of success. Although Kurumi's power was indeed tremendous, if Mio Suginomiya had granted her this strength, wouldn't she have some way to counter it? In Kurumi's memories, she had rarely seen Mio Suginomiya take action because, apart from the first time when Mio Suginomiya saved her, the battles afterward mostly involved her setting up barriers or handling other auxiliary tasks such as aftermath management.
Under these circumstances, it was easy for Kurumi to believe that Mio Suginomiya lacked combat ability.
But the truth was obviously not the case, because after Kurumi discovered Mio Suginomiya's secret, she was instantly "killed" by Mio Suginomiya.