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.
Turn down sex, but keep your true love.
Start your Adventure with Diana.
Be Baptized by Angels.
Be Eaten Alive by Diana's Pit Beast.
Obtain True Freedom.
Get Shot in the head by Malix.
Witness Simon's Transformation with Diana and someone special...
Impress the House Party Guests.
Preview the start of Seduce Me 2: The Demon War!
Rename the Main Character.
Get Proposed to by Andrew.
Go To Paris with Naomi.
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.
Get Proposed to by James.
Obtain True Power.
Unlock the Second Set of Bloopers!
Fight Malix Yourself.
Find Harold Anderson's Magic Books.
Unlock the First Set of Bloopers!
Dodge Malix in time.
Prologue Completed!