Ijiwaru na Haha to Ane ni Urareta Watashi. Nazeka Wakagashira ni Dekiai saretemasu

Sumire, who grew up being abused by her own mother and sister, was not allowed to go on to higher education, and all the money she earns from holding down jobs is taken away by the two spendthrifts. When she returned home, she was worked hard without a moment's rest, and the only solace she had was time to read books. Then one day, a yakuza gangster, claiming to be a young leader of the Shizuki clan, comes to collect on a debt her sister has incurred! (Source: Kadokawa, translated)