Yuuki's smiling at Arthur with her face covered in blood splashes from the severed cock in front of her had made Arthur feel that Yuuki had the talent to become a Yandere.
A talent that Arthur had just realized and with all his might Arthur wanted to hold back her.
If that talent continued to develop without proper supervision, Yuuki would end up torturing Niko physically and making him a masochist covered in physical wounds.
The kick that Yuuki had done earlier had also indicated Yuuki's emotions that were channeled well through the encouragement given by Arthur until her stress was channeled well.
"I have completed what my Master wanted," said Yuuki with a smile on her face that showed satisfaction after she had succeeded in cutting off the erect cock in front of her eyes.
