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