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