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 Eaten Alive by Diana's Pit Beast.
Obtain True Freedom.
Be Baptized by Angels.
Get Shot in the head by Malix.
Start your Adventure with Diana.
Kiss Erik under the Moonlight.
Give Damien his Humanity.
Share some Cake with Matthew.
Accept Sam for the Man he is.
Prove Your Love to Suzu.
Go To Paris with Naomi.
Get Proposed to by Andrew.
Fight Malix Yourself.
Witness Simon's Transformation with Diana and someone special...
Preview the start of Seduce Me 2: The Demon War!
Get Proposed to by James.
Turn down sex, but keep your true love.
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.