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