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.
Get Shot in the head by Malix.
Impress the House Party Guests.
Be Eaten Alive by Diana's Pit Beast.
Start your Adventure with Diana.
Obtain True Freedom.
Obtain True Power.
Get Proposed to by Andrew.
Go To Paris with Naomi.
Prove Your Love to Suzu.
Fight Malix Yourself.
Give Damien his Humanity.
Share some Cake with Matthew.
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.
Dodge Malix in time.
Kiss Erik under the Moonlight.
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.
Witness Simon's Transformation with Diana and someone special...