Here is the full list of all 25 Seduce Me the Otome achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Obtain True Power.
Be Baptized by Angels.
Be Eaten Alive by Diana's Pit Beast.
Obtain True Freedom.
Witness Simon's Transformation with Diana and someone special...
Get Shot in the head by Malix.
Preview the start of Seduce Me 2: The Demon War!
Impress the House Party Guests.
Rename the Main Character.
Start your Adventure with Diana.
Get Proposed to by Andrew.
Go To Paris with Naomi.
Prove Your Love to Suzu.
Fight Malix Yourself.
Dodge Malix in time.
Give Damien his Humanity.
Find Harold Anderson's Magic Books.
Share some Cake with Matthew.
Accept Sam for the Man he is.
Turn down sex, but keep your true love.
Kiss Erik under the Moonlight.
Get Proposed to by James.
Unlock the Second Set of Bloopers!
Unlock the First Set of Bloopers!
Prologue Completed!