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