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