Liu Zhenhan's visit to the human world this time had no expectation of reaching any wish or agreement with the Holy Vatican, which was evidenced by the fact that Vieri didn't accompany him back in Feilengcui.
This time it was more like a fortuitous event. Liu Zhenhan's initial plan was to coerce a priest to return to the Bimon Kingdom after coming back from the Underground World, but now before he could even reach the underground, he found himself pacified — though it was said to care for the little Nun, it was more like she torturing Liu Zhenhan with language.
Considering the benefits of the sacred auxiliary magic, Liu Zhenhan accepted the arrangement.