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