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