Isaac and the Black Sword Knights are responsible for training the Maihama army. While he's in Maihama Isaac gets to know the new crown prince of Maihama, a young boy named Iselus.  Iselus respect looks up to Isaac and respects him.
At a party for the crown prince's birthday, assassin's make an attempt on his life.
Don't worry about that, Sister.
Dann gibt es kein Problem, Schwester.
No te preocupes, hermana.
Dans ce cas-là, grande sœur,
soyez tranquille.
Non preoccuparti, sorella.
Não se preocupe, Onee-sama.
Тогда мне не о чем волноваться, сестра.