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