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