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