Oshikake Inumimi Dorei ga, NEET na Daieiyuu no Osewa wo Suru you desu.

A tale of a young girl who believed she was rubbish and had given up on attaining happiness, received training from the great hero. [My name is Maiya. 12 years old. From now on, I will devote my everything to serve master!] While spending a slow retirement life, the former hero [Thousand Dragon Killer] Rein, was visited by the beastkin young girl one day. Rein unwillingly agreed after the young girl said that she wanted to repay the favour for saving her life by serving him. The two are living life full of energy despite their differences. During this time, Rein noticed the hidden talent of the young girl. From a relationship of master and servant to teacher and student, this is a story of the new life of the great hero who lost everything and the young girl with nothing to lose Source: NU