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