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