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