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