Japanese copyright law protects all works "in which thoughts or sentiments are expressed in a creative way, and which falls within the literary, scientific, artistic or musical domain." The laws automatically provide the following rights, without the need for formal declaration or registration.^[https://en.wikipedia.org/wiki/Copyright_law_of_Japan]

Since the 90s^[1999 for Japan specifically], Copyright in the USA and all trade partners they have leverage over^[This is a general statement. Please research particular locales for specific situations per country], copyright has been automatically applied to all works without the need for registration. A creator can voluntarily put their work into the public domain, but this is an extra step they must do themselves. As a company, there's little reason to actually do this and give up your ability to protect your works and brands. Especially as a publicly traded company, you may even be putting yourself at risk for lawsuits by not profit-seeking as much as you can.

Strictly speaking, this very comment is under various levels of copyright, albeit the ability to protect it is both dubious and very unlikely.^[https://ipsolutionslaw.com/copyrights/photographers-and-artists-beware-social-media-post-forfeit-copyright/]

"is there anything from Japan that I don’t have to feel guilty about sharing with my friends and family (but mostly friends)?"

If you're concerned about observing copyright law, then practically the answer is no. Literally, the answer is that any cinematographic work before 1954 in Japan is in the public domain. The highest rated anime from that time period would be Manga Futatsu no Sekai (Two Cartoon Worlds) which scores a 5.38 out of 10 on anidb.

A court case in 2007 ruled that works released before and in 1970 are protected by copyright until 38 years after the creator's death. Works beyond that are protected for 70 years after the author's death, or 70 years if they're not made under the name of a single author to the work.

TL;DR copyright is on almost anything you'd want to share from Japan until it's 70 years old. We'll see the Astro Boy anime hit the public domain in the year 2033.