The Yamamoto House was a small House from JAPAN. It seems to have been established a few generations ago.
During the 4th Sengoku Era, the house was almost completely destroyed by the Ashikaga House, leaving only Isoroku Yamamoto and Tarou Yamamoto as the sole remaining members. As the inheritance rules of most houses of JAPAN including Yamamoto dictate that only a man can become the leader of the House, it seemed that only Tarou could possibly restore it to its former glory. As Isoroku was one of the greatest archers of JAPAN and a valuable warrior, Ashikaga Choushin took Tarou hostage in an undisclosed location, forcing Isoroku and her few remaining allies to fight for the house that destroyed her family in the hopes that Choushin would eventually release her brother..
During the war with Oda, she tried and failed to kill the foreigner Rance and all her allies would eventually lose their lives in battle, sacrificing their lives to give Isoroku a chance to live and hlelp Tarou restore the Yamamoto family. Eventually, Oda defeated the Ashikaga and captured Isoroku. Since he was quite interested in her beauty, Rance quickly released her in exchange for her allegiance, and together they discovered the secret village where Tarou was kept. However they discovered that the village had long been destroyed on Ikkyuu's advice and the young Tarou killed among the rest.
Though Isoroku grieved for both her brother and her family name, Rance eventually helped her realise that if she had a son, he could become the new heir of the House (if the father agreed). Though she initially searched for a husband among different JAPANese clans, Rance eventually convinced her that though he was a foreigner, as soon-to-be emperor of JAPAN he was more than a fit partner.
After the events of Sengoku Rance, she was pregnant with Rance's child and eventually gave birth to Rangi Yamamoto, Rance's second son and heir to the Yamamoto name. In one possible future, Rangi was raised as a proper dedicated samourai that would help lead JAPAN to come to his father's aid.