Harumi (also known as the Quiet One, the Jade Princess, or Rumi) is the former princess of Ninjago and the founder of the Sons of Garmadon. After losing her parents during the rampage of the Great Devourer, Harumi was adopted by the Emperor and Empress of Ninjago. For years, she sought vengeance against the ninja for allowing her parents' deaths, and she admired Lord Garmadon, who killed the Great Devourer himself.

The ninja begin to safeguard Harumi and the Royal Palace when the Sons of Garmadon rise to prominence. After the palace is destroyed and her adoptive parents are killed, Harumi joins the ninja and is protected by Lloyd, who she fakes a close relationship with. After sabotaging the ninja's plans, she and the Sons of Garmadon seize the three Oni Masks and use them to resurrect Garmadon as a soulless incarnation of his former self. After the ritual supposedly fails, Harumi is arrested, but her act was successful and Garmadon is revived. The dark lord frees her and her allies from prison. She watches as Garmadon fights and defeats Lloyd in Kryptarium Prison, after which he creates the Colossus. Harumi pursues Lloyd and a young Wu, who is presumably killed with the original ninja after Destiny's Bounty is destroyed.

Harumi serves Garmadon as he rules Ninjago, often running missions for him to help hunt down Lloyd's Resistance. When a mental battle for the Colossus breaks out between Skylor and Garmadon, Harumi saves a child and his family from suffering the same fate as hers. Haru