He has invited some friends along, to drink sake, sing songs and play traditional Okinawan instruments on the windswept hill on the west side of the Pacific island. But the picnic, as Chibana and his friends understand very well, is doomed to be a failure: blocking their way, even if they make it through the crowd of left-wing protesters expected to show up in their support, will be a handful of American troops, several metal fences and as many as 1,500 armed Japanese riot police.
Why Mr Chibana's outing should provoke the combined might of the US and Japanese security forces is, at first, difficult to understand. The land indisputably belongs to him, having come down from his grandfather, who was killed by invading American troops during the bloody battle of Okinawa in 1945. For 20 years it has been leased out - but the lease expires at midnight tonight when, by Japanese law, the rights to the plot revert to its owner.
But this is no ordinary land dispute, as you appreciate when you round the hill leading up to it from the village. Mr Chibana's 200 square metres are slap in the middle of the Sobe military intelligence gathering installation, a sinister cluster of pylon-sized antennae, bunker-like buildings, and Keep Out signs owned and operated by the US Navy.
In Yomitan they call it "the Elephant's Cage", but by the standards of the other US bases on Okinawa, the Sobe station is really rather small. There are 29,000 US troops on Okinawa; the massive barracks, ports, and air fields which they maintain take up one-fifth of the island. While the ships and bombers are the property of the military, the land is administered by Tokyo as its contribution to the US-Japan Security Treaty. Thirty-two thousand landowners have given over their plots, most of them quite willingly, in exchange for a guaranteed income from the government's generous rents. But 3,000 of them - the so-called "anti-war landlords" - refuse to sign the lease papers. Among them is Mr Chibana.
For 27 years this didn't matter. Until 1972, Okinawa was ruled directly by Washington, and the US military governor had the power to commandeer land at will. Even after reversion to Tokyo, it was not a problem - the governor of Okinawa was empowered to force the lease ofland. Then, in September last year, everything changed after a 12-year-old local girl was gang-raped by three US servicemen. The crime, and what was seen as the Americans' lackadaisical response to it, ignited long-standing resentment of the US presence, both on the island and throughout the country. When the time came for him to sign the lease documents for the land owned by Mr Chibana and his fellow pacifists, the Okinawan governor, a liberal academic named Masahide Ota, refused.
Officials shuttled frantically between Tokyo and Naha, the Okinawan capital, but to no avail. Mr Ota was ordered by a district court to give his consent. He refused again, and on Thursday the papers were finally signed by the Prime Minister, Ryutaro Hashimoto. Given the customary glacial pace of Japanese bureaucracy, the whole thing was resolved with remarkable, even suspicious, dispatch. But considerable paper-pushing remains to be done, and it has proved impossible to complete the procedure before the Sobe lease expires. For a couple of weeks, at the very least, the US military will be in illegal occupation of somebody else's land.
The bureaucrats in Tokyo already have a few ideas for avoiding this, all of which emphasise the remarkably vague and sweeping powers enjoyed by central government. In an "emergency", it appears, the government can seize whatever land it likes. Equally alarming is the principle being floated in briefings to journalists: that the US-Japan Security Treaty takes natural precedence over Japanese law. In peacetime, this is one thing, but in time of war, the implication that civilian laws can be overridden by the military requirements of a foreign power is far-reaching.
If all this weren't awkward enough, there is the added embarrassment of Shoichi Chibana. He is a rare thing - a pacifist and Japanese dissident, famous throughout the country for a stunning act of rebellion in 1987. At a national athletics meeting, he mounted the podium and set fire to the Rising Sun flag as a protest against its enforced use in schools. This year, he lost his final appeal against a suspended prison sentence for trespassing and damaging public property. To officials in Tokyo, the prospect of a famous radical tipsily singing peace songs on a top-secret intelligence base hardly bears thinking about.