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