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.
The weight of your responsibility 
is equal to the power you possess.
Ce sont aussi elles
qui le rendront plus fort.
Il peso di queste responsabilità 
è pari al potere che possiedi.
O peso da sua responsabilidade
И чем тяжелее её груз,
тем сильнее он становится.