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