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