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