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