Born Nagasada Mori in 1565, Ranmaru is the son of Mori Yoshinari (a head retainer under the service of Nobunaga Oda during the late Sengoku period of Feudal Japan. Regarded with great consideration for offering his son, Ranmaru, to be the head page under Nobunaga, Yoshinari was frequently granted rank and thus willingly supports his new lord within variable conflicts following the period at which he began his assistance to the Oda), and the younger brother of Mori Nagayoshi (an officer under the Oda clan), from the province of Mino.

From an early age, Ranmaru was an attendant to Nobunaga Oda. Recognized for his talent and loyalty, he was appointed to a responsible post (head page, and as such was always by Nobunaga’s side, during strategic meetings with other generals (highly unusual) and during battles, always at Nobunaga’s side; A valet's ultimate duty is to protect his master from any bodily harm, including in battle, as such Ranmaru became quite the competent swordsman).

At Oumi, he was given 500 koku, and after Takeda Katsuyori's death, he was awarded the 50,000 koku at Iwamura Castle.

Nobunaga and Ranmaru's lord-vassal relationship follows the shudo tradition, despite of Nobunaga’s marriage to Lady Noh.

Intuitive, Ranmaru Mori knows just what Nobunaga wants and when he wants it; the absolute demand of speed in Nobunaga's daily life - as far as his household is concerned - keeps everybody else in chaotic confusion with the exception Ranmaru; he is the only one fast enough for Nobunaga, who always expects his orders to be carried out before they were ever given.

In Rivelata:

Ranmaru has kept very much to himself. Upon his arrival he immediately sought passage home and tried recruiting experienced seamen to aid him. During this time he learned much from the people of Rivelata, their secrets, their history, and more importantly he learned about the Queen and her city.

He learned of Mistuhide Akeichi's ultimate betrayal from Sasaki Kojiro

Several weeks into planning their island escape, Nobunaga, Ranmaru's lord and general appeared on the island. Right away Ranmaru filled Nobunaga in on everything there was to know of Rivelata.

[in progress...]