Re the alleged 1984 lawsuit - The worst thing is that we don't even know which country the Japanese WP article and blog sites (found a few more) echoing the WP article are referring to. My assumption is that it was Japan, since the allegation can only be found there.
Alas the Japanese legal research help sites are a mix of broken links and paid services. The prime
free search tool seems to be
裁判例検索 | 裁判所 - Courts in Japan and I tested it by finding the Gibson vs. Fernandes case of 2000. That was the Tokyo High Court in times when the internet existed though, and the search site says that their records are incomplete - I guess 80s cases are just not fully recorded in electronic form.
"Fender" or フェンダー and 東海楽器研究所 (Tokai's company name until1986 ) brings up nothing relevant, neither does 東海楽器 with one exception I found kind of interesting (but alas irrelevant too): The name Tokai shows up in a 2007 infringement claim Fillmore Co. Ltd vs. Kurokomo (this is part of the messy "Moseley vs. Ed Roman and Mosrite Japan, Mosrite Japan vs the other Mosrite Japan" chain of legal disputes). Fillmore Co. Ltd is the appellant, Kurokomo the appellee:
In addition, since around 2000, the appellant has owned Tokai Musical Instruments Manufacturing Co., Ltd. located in Hamamatsu City, Shizuoka Prefecture
That would mean at that point in time (2007), Tokai was owned by Fillmore Co. Ltd / Yusa Noriyuki.
Back to the topic - I think a Japanese lawyer should know best how to retrieve such information in Japan, if anyone knows a guitar loving Japanese lawyer...
If that was something that happened in the US, that could've affected only Tokai USA and there should be a sign of it somewhere. Trying to find something in
https://www.fjc.gov/research/idb turned up nothing. What is "Tokai USA" anyway? Besides the obsucre IMC link, there was a Lakeview company and another one it seems.