
Question for spoiler
Okay, who is the old man? The king? Jaeshin's father? Just random old man? Thank you.

The old man appears at the very beginning and his story is literally the reason why Jaeshin got punished by his dad who turned him into a puppy in the mortal world lol The old man was gambling with Jaeshin and asked him to extend his life. Jaeshin played a game on him by taking his son's life to extend the old man's. Except he wasn't allowed to and his father punished him by sending him as puppy to the mortal world so he can learn some manners and grow a heart! In the meantime, the old man was plotting his revenge over Jaeshin. Of course he didn't take Jaeshin's life when the opportunity came but rather his precious partner just like he took his son! The season ending this way makes total sense. Now we have to wait for Season 4 and see what the author will be cooking for us :))
Bro has secured lifetime free rent just like that
Oh to be loved by he tian