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