I think Jumin has a more sophisticated world of his own, so I’m not sure if he’ll need your advice.
This Mystic Messenger Jumin walkthrough will ensure you gather the maximum possible hearts from the stoic CEO-in-line.
If you are playing Mystic Messenger in Casual Story mode, you cannot secure his route.
If you want to make sure you see the Jumin route at the end of this period, this walkthrough of the Prologue, Day 1, Day 2, Day and Day 4 is all you need.