Naofumi follows the slave merchant to his store, where he looks for a partner to act as his sword. But all he has the money to buy is a diseased demi-human girl named Raphtalia, whom he then forces into an incredibly harsh battle.
So that's why she starts 
crying every night.
لهذا تبكي إذاً في كلّ ليلة
È per questo che di notte piange?
É por isso que ela chora toda noite.