Deep Story is one out of the two modes available in Mystic Messenger, the other being Casual Story. Compared to Casual Story, Deep Story focuses more heavily on plot details.
Since it requires 80 hourglasses to unlock Deep Story mode, it is highly recommended for players to unlock all three routes available in Casual Story first before proceeding to Deep Story.
Because of this, both of them are not romanceable in Casual Story mode despite the player being able to obtain their hearts in Casual Story. Likewise, Yoosung, Zen and Jaehee will not be romanceable in Deep Story.
Deep Story: Bad Ending
If the player misses too many chats, or obtained only Yoosung / Zen / Jaehee Kang's hearts, or did not obtain enough hearts of either one of the two to get a route by Day 5, the player will obtain a bad ending at the start of Day 5.
Prior to Day 5, V informs Seven and the player that he will be taking a trip a week before the party's set date. Seven tells V that he installed a bug detector on his phone, where a red light on the phone will shine if a bugged call is detected. Right after the two log off after discussing the party, Unknown, who had hacked into the chatroom unnoticed, suddenly leaves a threat.
At midnight, V is in the mountains stargazing, reminiscing about Rika. He vows to be with her soon, and his thoughts are cut short when Unknown approaches him. Unknown had rummaged through V's luggage in his car, suspicious of his intentions. He suspects that V had planned on investigating the cause of why the player joined the messenger, and threatens him not to sabotage his group else he will plan a "surprise" for RFA, especially Seven. He then captures V and holds him hostage.
At Seven's house, while Vanderwood is cleaning, Seven is making homemade Honey Buddha Chips. He receives a call from V's phone, but discovers the call is bugged and that it is Unknown who is calling. At 1 AM, he quickly goes on the messenger to warn the player to leave Rika's apartment as soon as possible because the bomb inside will detonate at any moment. As for Seven, he resolves to save V and plans on calling Jumin to send bodyguards to protect the rest of the members. Because of the sudden emergency, RFA is unable to host the party.
The player is confused, but Seven hastily reveals that there is a "force" targeting the documents in Rika's apartment and V, the leader of RFA. Furthermore, RFA is hiding secrets that he feels the player is better off not knowing, and he tells the player not to involve herself in the organization anymore for the sake of her safety. As the player and Seven exchange farewells, the player is unregistered from the messenger.