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