The Hakone Incident, also known as the Sankai Resort Incident or the Battle of Hakone was an international incident resulting from a four-way engagement between the Japan Self-Defense Forces, US CIA Special Operations Group, The Russian CPB, and the Chinese MSS. The latter three forces intended to capture the visitors from the Special Region who were housed at the Sankai Resort in Hakone, Japan, in order to gain intelligence about the region and use them as bargaining chips to force the Japanese government into granting them access to the Gate.
Due to faulty intelligence from the higher-up, the initial engagement occurred between the Japanese Self Defense Force Special Activities Division forces and the CIA Special Forces caused at least a few members of each unit were killed. Furthermore, due to Japan strict border control policy, most of CIA members are under-equipped, forcing them to smuggle weapons and purchased military support hardware from local civilian tourist shop, making them lack the advantage to deal with JSDF Special Force effectively due to the lack of access to their standard equipment. Additionally, some of the CIA members arrogantly forgot about the fact that the JSDF Special Force used to received training from US Special Force in the past, which makes the JSDF Special Force as good as CIA.
However, the JSDF forces were ordered to retreat after the CIA blackmailed Japanese Prime Minister Motoi into removing the JSDF guards with threats of releasing evidence of corruption within his Parliament. With the JSDF guards removed, the US, Russian, and Chinese special forces encountered each other, leading to a chaotic three-way firefight. Rory Mercury, who was at that time staying in the hotel with the Third Recon Team and the other visitors from the Special Region, armed herself with her halberd and joined the fray, causing further casualties. Between the firefight and Rory's intervention, the few still living foreign Special forces were annihilated in a matter of minutes.
In order to avoid a scandal of the recently revealed corruption, Motoi resigned shortly before news of the scandal reached public exposure.
The Third Recon Team seized weapons from the fallen agents and escaped along with the visitors to the region, along with Risa; notably, Piña, with the help of Bozes, tried a scheme by smuggling a couple of guns to present to her father, but this failed later when they were searched by JSDF personnel prior to crossing the Gate back to the Special Region.
As the visitors were set to return to the Special Region, all three foreign special forces plotted a second attack in an attempt to capture the girls at the Gate's threshold in Ginza. The attempt failed because a blog posted by Aoi Risa on the internet attracted thousands of civilian witnesses intent on seeing the visitor from beyond the Gate. The large number of witnesses made covert actions impossible, and the Special Region envoys returned without incident. Shortly afterwards, all three foreign powers ordered their covert agencies out of Japan and denied any responsibility for the incident.