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