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