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