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