Final answer:
The Yakuza is the group that controls most organized criminal activity in Japan, with a complex structure and deep roots in Japanese history.
Step-by-step explanation:
The group that controls most organized criminal activity in Japan is the Yakuza. The Yakuza is known for its strict codes of conduct and hierarchical structures. It has its roots deep in Japanese society, stretching back to the Edo period, where societal structures were quite rigid.
The Yakuza, also referred to as Boryokudan or Gokudo, evolved not just as a criminal organization but also a cultural phenomenon, involved in various businesses, both legitimate and illegitimate. While terms like 'Boryokudan' and 'Gokudo' are often associated with the Yakuza, the former is used by the Japanese police to classify such criminal organizations formally, and the latter refers more to the way of life or philosophy of Yakuza members. Meanwhile, the Triads are generally associated with Chinese organized crime and are not the main group operating in Japan.