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