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.
Be Baptized by Angels.
Be Eaten Alive by Diana's Pit Beast.
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!
Start your Adventure with Diana.
Get Proposed to by Andrew.
Obtain True Freedom.
Impress the House Party Guests.
Prove Your Love to Suzu.
Give Damien his Humanity.
Share some Cake with Matthew.
Accept Sam for the Man he is.
Dodge Malix in time.
Kiss Erik under the Moonlight.
Turn down sex, but keep your true love.
Get Proposed to by James.
Go To Paris with Naomi.
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.