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