Koishita Hito wa, Imouto no Kawari ni Shindekure to Itta

Koishita Hito wa, Imouto no Kawari ni Shindekure to Itta is a Manga/Manhwa/Manhua in (English/Raw) language, Drama series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.com fastest updating comic site. The Summary is

In place of her sister, Wisteria is a former daughter who has become a guardian of a poison-filled otherworld. One day, a man who resembles her first love appears from the sky. His name is Lloyd. To her surprise, he is the son of her first love! As a proof of his marriage proposal to the princess, he has come to ask for Wisteria's partner, Sartis, a holy sword that can understand words. Having survived in a frozen time, she tells him to defeat Lloyd with her own magic and return to her own world. I will take you as my apprentice so that I can defeat you! But, despite his efforts to persuade her, she is forced to stay. The relationship between master and apprentice begins one-sidedly, with the apprentice learning magic as she goes along. Will her time, which has remained frozen, begin to move again? A master-student love fantasy between a lonely former daughter and a genius nobleman!