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