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