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