Special Investigation Team

The are specialized detective units of the Prefectural police headquarters (PPH) of Japan, mandated for critical incidents including crime investigation and even SWAT operations.
History.
In the 1960s, the increase of serious criminal cases such as kidnapping, aircraft hijacking, piracy and bombing became a serious problem in Japan. The , a four-year-old child, raised significant questions to solve these kind of cases. In this case, , a detective assigned to the case, was able to apprehend the suspect, but it was too late to save the victim.
It became clear that traditional criminal investigation systems were sluggish and outdated for these new-style, rapid-tempo, and sometimes lethal cases. As a response to these problems, the Tokyo Metropolitan Police Department (TMPD) established the SIT unit within their Criminal Investigation Bureau in 1964. These detectives were well acquainted with new technology and special tactics to track and capture the criminals quickly and accurately.
At the beginning, the name "SIT" came from an acronym of its romanized Japanese unit name, , but later, the origin of its name as an acronym of its English nickname, Special Investigation Team, was added afterwards by misunderstanding from an officer who is fluent in English.
This idea achieved a great success that in 1970, the National Police Agency (NPA) requested the establishment of these kind of units for other Prefectural Police forces throughout Japan. These detectives also became responsible for intervening and rescuing when hostages were in danger. In 1992, TMPD strengthened the SWAT capability by incorporating several SAP operators into its SIT.
Organization.
Structure.
All unit are established in the of each Prefectural police headquarters (PPHs). These units are generally local-based, so organizations (including their unit names) and equipment are varied. Among them, the Special Investigations Team (SIT) of the TMPD and the Martial Arts Attack Team (MAAT) of the Osaka PPH are the first units to be created and still the most prominent units nationwide even now.
In the First Criminal Investigation Division of the TMPD, the following units are assigned for special criminal investigation activities:
Of all these units, Units One and Two are in charge of hostage cases and especially known as "SIT". As of the early 2000s, there were over 60 detectives in total for these seven units, and about 30 detectives with Unit One and Two alone. On the contrary, some rural PPHs assign only one or two detectives to these offices, so in case of SWAT operations, these units can be reinforced by detectives of , first responders for initial criminal investigations. 
When these rural PPHs were faced with critical incidents requiring a special investigation, the NPA ordered the TMPD or Osaka PPH units to dispatch advisers to the relevant PPH customary. And later, this custom evolved into the as a formal institution of the NPA, being made up of experienced detectives selected from across the country. These detectives usually work at their respective PPHs, but they may be dispatched to other PPHs to provide advice to the local commander as needed.
The Task Force also conducts research on special investigations, such as participating in training at the Federal Bureau of Investigation of the United States, and regular joint training sessions are held to disseminate its outcomes. And the SIT of the TMPD has also received advice on SWAT operation from the Far East Field Office of the Naval Criminal Investigative Service in Yokosuka.
Capabilities.
For manhunt missions, detectives of these units are well acquainted with many technique and technology such as telephone tapping, stakeout, surveillance, and crisis negotiation. And in order to restrain violent criminals quickly, they also have tactical capabilities. In addition to standard service handguns (.38 Special caliber revolvers such as New Nambu M60, or .32 ACP caliber semi-automatic pistols such as SIG Sauer P230), some units are equipped with large 9×19mm Parabellum caliber semi-automatic pistols (Beretta 92 Vertec, for example) and pistol-caliber carbines (Heckler & Koch MP5SFK, semi-automatic variant of MP5K with foldable stock). They also use non-lethal weapons such as FN 303 or BGL-65.
Counter-terrorism operations are the affairs of the operators of the Security Divisions, such as Special Assault Teams (SAT) or Anti-firearms squads, so these SWAT-capable detectives are mandated for critical incidents except terrorism. However, in some rural but well-versed Prefectural Police like Aomori, these detectives can form a counter-terrorism task force together with uniformed officers and riot specialists.