I would have killed the demon already. This world is too young yet and Yuan is still too powerless (and injured) for his earlier self to play around for too long.
i think there may be other demons on earth, or maybe a portal that leads to nine heavens, since the demon knows about the demon sealing clan and its founder, which was mentioned in Cultivation Online.
Thanks for the chapter!
Yaun will eat the demon core to regenerate the hole in his chest. But won't the core fall off from the hole when he swallows it since the hole is in the centre of his chest, unless the core is absorbed in the mouth itself...