This is a text message in Zen's route, Day 9. Should I not really receive any reply from him or is this some kind of bug? The same thing happened in Jumin's
Mystic Messenger Zen route guide - Gamepur
Mystic Messenger Zen route walkthrough and endings guide- Day 5, 6, 7, 8, 9, 10 and 11 (Casual mode) | VG247
Mystic Messenger Jaehee route chat times schedule - Days 5, 6, 7, 8, 9, 10 and 11 (Casual Story mode) | VG247
Zen/Endings | Mystic Messenger Wiki | Fandom
Mystic Messenger - ZEN ROUTE || Day 9 (Part 2) - YouTube
Mystic Messenger - ZEN's Route Day 5 to Day 10 (GOOD END) - Jin's Records
The most boring route? : r/mysticmessenger
Walkthrough Mystic Messenger: Zen ~ Day 5 | CapiOra