Schuld 
Min-Maxing My TRPG Build in Another World: Volume 2 [EPUB ebook] 

The magus Agrippina saves the munchkin hero Erich by the skin of his teeth. But this favor does not come without a cost—she brings news that little Elisa is actually a changeling! To protect his sister’s future, Erich’s only choice is to accompany the magus to the imperial capital as a servant, leaving his hometown behind…but not before making an oath to his childhood friend. When fairies suddenly appear on his path to the capital, will he be able to avoid a critical failure?! The Henderson scale-breaking, number-crunching TRPG adventure returns for another session!