I have a query regarding a tale, probably a legend, about an 18th-c. figure of Japan, named Chunosuke Matsuyama.
I have been researching a legend, according to which Theophrastus used drift bottles to demonstrate the Gibraltar current. Nearly always cited with that legend are some others, among them (since 1948 at least) is the tale that, with 43 companions (some accounts have "44"), Chunosuke Matsuyama was shipwrecked in 1784, and sent out message(s) in bottles, one of which was found in 1935 or so, in his own hometown; e.g., see the National Geographic (http://news.nationalgeographic.com/news/2012/09/120918-oldest-message-in-a-bottle-science-...): "And in the 18th century, a treasure-hunting seaman from Japan named Chunosuke Matsuyama, shipwrecked on a South Pacific island with 43 shipmates, carved a message into coconut wood, put it in a bottle, and set it adrift. It was found in 1935 — supposedly in the same village where Matsuyama was born."
(I have already been aided by a few speakers of Japanese (among which I am alas not one), who are the source of the hiragana and other similar data below.)
The name "Chunosuke" (spelled phonetically in Japanese as ちゅのすけ) seems quite rare, and the ending -suke may be represented with either the character 輔 or 助, both of which mean "help, rescue, assist" – so I wonder if the name could refer to the tale? (I.e., it is a fictive and "ominous" name.)
The National Geographic doesn't include the name of his village (or the date "1784"), but other sources regularly give "1784" (one source says "1714"), and these three give a name for the village:
* Wilmon Menard, “Neptune's Sea-Mail Service,” Sea Frontiers 26.6 (1980) 336–340 at 337 says "Hiratamura"
* Robert Kraske, The twelve million dollar note: strange but true tales of messages found in seagoing bottles (Nashville: Nelson, 1977) 40–42 says "Hiraturemura" (but "tu" could not be a Japanese sound).
* http://www.histarmar.com.ar/Prefectura/REVISTA-GUARDACOSTAS/ElCorreodeBotellas.htm has "Matsoyama" and "Hiratatemura" (and "1936")
Also, I have come across a reference to a Japanese encyclopedia of drifted objects, which *might* contain data about Matsuyama, if he was real, and if the encyclopedia goes back far enough? See: http://www.newsweek.com/treasures-sand-142347
Moreover, Ebbesmeyer and Scigliano, Flotsametrics (2009) make no mention of Matsuyama, but 54–55 do cite the tale of the poet Yasuyori (from 1177) in the Tale of the Heike. So it's not the use of drift-vessels (in the case of Yasuyori, I think just planks?) that I doubt, but that there was a specific such drift-vessel sent by anyone named Matsuyama.
So – my question here is, is there any evidence in Japanese-language sources for the actual existence of Chunosuke Matsuyama, or is there perhaps even a Japanese-language source that either provides the source of the fiction, or at least analyses the data and concludes one way or the other about the reality?