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