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