悪魔殺害者を抹消してください
To exterminate or to eradicate in Japanese is tayasu [絶やす]
demon blade in Japanese is akuma no tsubasa
ma o
no spells are needed, all that is necessary is to defeat the demon with silverlight and say the correct words.
ダークデーモン
saigo no enjerusureija
It's different for everyone, you should have payed attention during the quest because it tells you word for word.
ma o
Hi no akuma
aoi akuma
Furasshu no akuma
'Beautiful demon' would translate to 美しい鬼 (utsukushii oni) in Japanese.