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.
Obtain True Power.
Get Proposed to by Andrew.
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.
Witness Simon's Transformation with Diana and someone special...
Preview the start of Seduce Me 2: The Demon War!
Go To Paris with Naomi.
Prove Your Love to Suzu.
Get Proposed to by James.
Start your Adventure with Diana.
Impress the House Party Guests.
Be Baptized by Angels.
Be Eaten Alive by Diana's Pit Beast.
Dodge Malix in time.
Get Shot in the head by Malix.
Find Harold Anderson's Magic Books.
Obtain True Freedom.
Fight Malix Yourself.
Rename the Main Character.
Unlock the Second Set of Bloopers!
Unlock the First Set of Bloopers!
Prologue Completed!