Hyaku Ryuu Koroshi to Bukiya no Youjo - Iseki Tansaku ni Onnanoko ga Tsuite Kuru no wa Naze Darou ka

There is a problem in Avenue, a fierce adventurer with a reputation as "Devil Murder". As a result of a magical operation being too superior, weapons cannot bear, frequently break, and living expenses are insufficient! In addition, because of his scary appearance, one boy could not find a partner. One day, he fell in love with a single girl, Lilyisha (12 years old) of a weapons workshop who helped him by chance. However, the studio where she worked on was on the verge of bankruptcy due to debt.

(Source: mfbunkoj)