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