This sounds like he did not file correctly what is known in the USA as SEC Form 4, “Statement of changes in beneficial ownership of securities,” from 2010 to 2015.
The company assets in question appear to be residences Nissan acquired for him in Brazil and Lebanon.
Regarding "mis-use of Nissan funds," yes, it sounds like he pitched to the board that they should spin-off a startup incubator/investor firm, but then he directed the new firm to purchase houses for his use. However, I haven't read any report that ownership of the properties was transferred to him. So there would be no "change in ownership of beneficial securities." At most, you could fault him for not declaring the value of his use of the properties. Depending on how you look at it, he benefited from their use for several days per year, or they were de-facto leased to him. But he didn't own them. This is clearly shady, but I don't think this is beyond-normal for a Japanese Zaibatsu. In fact, we have state legislators in the US living in houses that were paid-for by utility companies in their home state, with no later findings of any criminal wrongdoing. I am dubious that a typical board chair at a Japanese corporation would be called-out for staying in a "guest house" paid for by the company.
The misreported income and the separate problem of the misuse of corporate funds (the properties) may have been conflated in the CleanTechnica article. MarketWatch describes the "misreported income" as something separate from the properties:https://www.marketwatch.com/story/ghosn ... 2018-11-28
It reports that Ghosn, as board chair, could set is own salary, without notifying the board (legally); and that he "wrote IOUs" to himself (unclear what such an "IOU" looks like). The article describes that he awarded himself some "deferred compensation" which quadrupled his salary (but was deferred, not paid). Deferred compensation would have had to have been recorded as a liability on the Nissan books. But for US taxes, it would only be accounted-for when it is paid; not when it is promised. Deferred Compensation is at "substantial risk of forfeiture": if Nissan went bankrupt, the money is gone. If Nissan was acquired (even by Renault!), the money may be gone. I have no idea how the filing to Tokyo Stock Exchange treats deferred compensation, but it's not the same as compensation. Since he never received the money, the case is complicated.
My suspicion is that Nissan's board already got what it wanted (Saikawa-san as board chair). They may want a conviction (for something, anything) to smooth things with Renault, who is still 42% shareholder. If they release Ghosn after 14 days with no charges, the next board meeting is going to get ugly.