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