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