Because
As the river god of Mitsui River, Mitsui Jing felt that he couldn't bear it anymore.
Who can bear to watch a Mary Sue throwing severed limbs into her river every day?
So she went up and tried to freeze Mary Sue into a human stick, but was targeted instead.
Mitsui Kagami: Gan!
Mary Sue: Do you know about the Bliss Cult?
So
Mary Sue unswervingly took Mitsui Mirror to eat and drink in the Paradise Sect.
Mitsui Kagami: This is not a believer of mine... It smells so good!
Mary Sue: We must always be together XD
later
River God and Mary Sue live happily together forever.
Purpose: redemption