Here is the full list of all 31 Otome the Exorcist achievements.
Completed the first dungeon.
Beat the game.
Defeated 30 enemies.
Defeated 60 enemies.
Defeated 90 enemies.
Defeated 120 enemies.
Defeated 150 enemies.
Defeated the Park Nest Boss.
Defeated the City Library Boss.
Defeated the Beach Nest Boss.
Defeated the Abandoned Building Nest Boss.
Saw the Apartments Nest Boss being defeated.
Defeated the Takemaru Laboratory Nest Boss.
Defeated the Kureha Mountain Nest Boss.
Defeated the Himori Mine Boss.
Defeated Youma Roselia.
Defeated the Cultists in the Sacrificial Room.
Defeated the Trash Mountain Boss.
Defeated the Mushroom Mountain Boss.
Defeated the Takemaru Building Boss.
Defeated the final boss.
Relaxed in the shower after a long day.
Provided some hot buns to someone who needed them.
Did what was expected of you.
Visited the beach and met an acquaintance.
Thought about what has happened while on the roof.
Saw Mei having fun at the park.
Saw Mei killing time.
Saw Nanako gain Animus.
Saw Caps's manager preaching to her.
Saw how much Leone loves her ramen.