When returning to the sect... he feared sabotage by alien races, even though the likelihood was low, it wasn't absolutely safe.
Excluding those two places, the remaining option was Blue Mountain, which Su Yu also leaned towards returning to.
There are three reasons.
First, it's been a long time since he returned, over ten years; it's just the right time to visit family and friends.
Second, Blue Mountain is the heartland of humanity, it's absolutely safe there, no matter how grand the tribulation there is no risk of alien disturbance.
The third reason is naturally to return home gloriously; he's become so powerful, about to transcend into immortality, it's normal to show off a bit back home.
So...
Su Yu opened the regional channel of Beiming Dragon City and sent a message:
"Does anyone know a quick way to travel to and from the human heartland?"
In less than ten seconds, someone replied:
