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