Here is the full list of all 78 Novena Diabolos achievements.
Arrived at Hope Hill Motel
Clear the prologue
Met a certain someone for the first time
Heard the villagers talking about the abandoned school
Took a closer look at all the characters
Endured the pain of thorns being pulled out
Reached good ending with Sumi
Reached good ending with Rin
Reached good ending with Nari
Met the motel owner on your way back with Mina
Experienced complicated feelings about Hoseok Cho
Reached good ending with Hana
Asked Mina about the game's story
Reached bad Succubus ending
Asked Mina if she had a bad dream
Reached bad Fox Spirit ending
Obtained all hidden collections
Reached bad Witch ending
Suggested leaving the village to Nari
Reached good ending with Mina
Reached bad Undead ending
Had a conversation about the past with Nari
Reached bad Vampire ending
Witnessed the attack on Sumi
Called Sumi 'heavy' while carrying her
Answered all of Hana's questions correctly
Obtained all Succubus Investigation Records
Obtained all Fox Spirit Investigation Records
Obtained all Vampire Investigation Records
Stayed patient despite Rin's tirades
Obtained all Witch Investigation Records
Obtained all Undead Investigation Records
Got info about the cult and talked to Hana
Completed the whole Monthly Maxine collection
Collected all available information about the monsters
Obtained all pieces of info about the village
Completed the whole Monthly Satanism collection
Brushed off Rin's concerns
Had a run in with the wild boar