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