Noir is the 3rd son of a poor noble and his job position is taken away by a more powerful noble. He also sadly lacks enough skills to attend the Hero Academy. He tries to find a way to be able to use his skill [Great Sage] better and stumbles across a hidden dungeon.
And that's why I came to 
the third floor, but...
...ولهذا أتيتُ إلى الطابق الثّالث، لكن
Ecco perché sono salito al terzo piano, però...
Por isso vim até o terceiro piso, mas...
Поэтому пошёл на третий этаж...