Barthel

 (バルテル, Baruteru) was a former slave who was bought by Mukoda Tsuyoshi to work in his business.

History
Barthel was once an adventurer who, in a certain quest, didn't use his special weapon thus he was turned into a slave as a penalty as he wasn't able to pay the penalty fee.

In the House of Mukoda, he acted like a teacher along with Tabasa, using his vast experience and knowledge.