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