See also:
   • Japanese Defence Force base: Kubura, ...   and    • yonaguni: ENE of higawa with kubura i...  
The Okinawa archipelago stretches from Kyushu, the southernmost main island of Japan, to Yonaguni, less than 100 km east of Taiwan: the mountains of Taiwan can be seen from Yonaguni on a clear day. Yonaguni is due west of the Yaeyama island group in the Japanese Prefecture of Okinawa, over 500 kilometres southwest from Naha, the capitol of the main island Okinawa (the site of the most famous and bloodiest battle of the Pacific War 70 years ago, and the current site of the majority of US military bases in Japan).

The video shows the new military base under construction in Yonaguni, along the southern-most road running east from Kubura, the Western-most point of Japan. This will serve (see the last link) as an essentially proxy US base for its so-called ‘pivot to Asia’:

According to diplomatic cables released by Wikileaks, the (now not-so) recent visit of US warships to Yonaguni was intended as the ‘thin edge of a wedge’ for the later use by US warships, as required. The US believes the harbour is currently large enough to accommodate four mine sweepers: the scale of new construction dwarfs any currently existing facilities on Yonaguni.

The new Japanese Defence Force base is being built in what was previously one of the most beautiful parts of the island, and is of course funded by Japanese tax payers. Some have suggested that an additional role to be played is for possible defence of US bases in Japan, of which the vast majority are located on the main island of Okinawa, where there are currently many opposed to the construction of a new US base at Henoko.

For more information on the strategic role of Yonaguni, see the comments by
Kevin K. Maher,
former Consul General, U.S. Consulate
General, Naha, Japan, Department of State
in the Wikileaks-released cable:

cables.mrkva.eu/cable.php?id=113566

and the article by Gavan McCormack:

japanfocus.org/-gavan-mccormack/3837/article.html

Some have argued the potential threat from Taiwan for future conflict with Japan: this would appear less likely than conflict directly with China, since both governments - of Japan and Taiwan - still currently act to serve US interests, especially the former. The more likely access to the Pacific Ocean sought by future Chinese fleets is via the gap between the Yaeyama Islands and the main island of Okinawa, thus near to the disputed Senkaku/Daioyu islands (assuming they acquire ships in adequate numbers — currently they have one aircraft carrier, refurbished from the previous Soviet Union). The more cynical may view militarisation going hand in hand with escalation of the Senkaku/Daioyu islands dispute subsequent to the following cable:

cables.mrkva.eu/cable.php?id=215189