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