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