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