Seiichi and Saria train under Artoria to become adventurers. During their training the three of them are teleported into a dungeon by a demon’s trap.

The dungeon they find themselves in the stronghold of the Black Dragon God, the strongest member of the Demon Lord’s Army. Artoria gets separated from Seiichi and Saria in the dungeon and the giant Black Dragon God appears before her. Then that overwhelming threat attacks! Can Seiichi and Saria save her in time?!
He's renowned as the strongest 
one in the Demon Lord's army.
إنّه معروفٌ بكونه الأقوى
في جيش ملك الشياطين
Man sagt, dass er der
stärkste in der Dämonenarmee ist.
Es el más poderoso de todo
el ejército del Rey Demonio.
Es el más poderoso de todo
el ejército del Rey Demonio.
Notre maître le considère
comme l’ultime atout de notre armée.
È noto per essere il più forte
nell'esercito del Re demone.
Ele é conhecido como o mais forte
do exército do lorde demônio.
Его считают сильнейшим 
существом армии демонов.