This is the WEB NOVEL version. There is also currently a LIGHT NOVEL version that has been written differently from the web novel, although the overarching plot is the same.
Translations can be found here: https://yoraikun.wordpress.com/7s-chapters/
Lyle Walt is a young noble boy and heir looking forward to the day he can inherit his family's territory. Except around when he was 10 year old, his parents started neglecting him more and more in favour of his little sister, Celes. On his fifteenth birthday, he is challenged to a duel by his sister to see who will inherit the household and horribly loses, being cast out of his family. Afterwards, he gets treated by the family's groundskeeper and receives the family heirloom Gem from him that Lyle's grandfather had entrusted to him. From there, he begins his journey with his childhood friend and former fiancée, Novem, and the Gem-turned-Jewel that houses the memories, personalities, and Skills of seven of his ancestors.
*I neither own nor take credit for anything related to this story (including translations)