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