@Milanin both are technically correct. He's using the Japanese pronunciation of the English word "sun."
But still, since his in-game name is in romaji it should also be used for the translation in my opinion.
@alacaelum They are still mortals with base desires. Taking into account that the MC and the characters around him are from a demonic sect things will naturally be more chaotic. Cultivation itself is no easy road and requires extreme will, if not obsession, so cultivators will naturally be...
So I'm guessing the cultivation technique the senior sister is looking for is the one Mo took from the Xia ancestor in the cave? That soul eating one or whatever.
This is going to get messy.