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