Charlotte: Toaru Jijo no Shiro Tsukae Monogatari

Her parents disappeared a year ago. The girl was left alone and spent her days working at the castle. She returned to her parents' home on her days off to prepare the house for her parents' return. One day, when she returned home, she found a stranger there! Charlotte clutched her wooden sword in trembling hands...!

(Source: Gangan Online, translated)