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