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