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!
Start your Adventure with Diana.
Be Baptized by Angels.
Obtain True Power.
Rename the Main Character.
Witness Simon's Transformation with Diana and someone special...
Be Eaten Alive by Diana's Pit Beast.
Find Harold Anderson's Magic Books.
Obtain True Freedom.
Get Proposed to by Andrew.
Go To Paris with Naomi.
Prove Your Love to Suzu.
Fight Malix Yourself.
Give Damien his Humanity.
Share some Cake with Matthew.
Impress the House Party Guests.
Accept Sam for the Man he is.
Kiss Erik under the Moonlight.
Get Proposed to by James.
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!