Using the word "nintendo" on something intended to play any kind of games is trademark infringement. The Kawaii devs likely don't intend to confuse people, but if a consumer saw this product for sale they'd rightly assume it's a Nintendo product.
Using a brand name like this just makes things easier when Nintendo attorneys barely have to roll out of bed when sending a cease and desist order.
Just call it Kawaii and stay slightly under the radar. Sadly, Nintendo will probably come for you anyways.
Many years ago I bought an Intel processor. It came with a sticker inside a book that was several pages of terms and conditions on what the sticker can be stuck on. Mentioned as something not to do was applying the sticker to a computing device that did not contain an Intel processor, so I immediately stuck it on my Switch.
Some of these console mods only really get sold as kits or products on places like Aliexpress.
Needless to say, they are pretty safe from Nintendo. If these guys aren't selling the schematics, and posting them for free, Nintendo has a lot less of a leg to stand on.
Nintendo is notoriously litigious. It is naive to think you’re “pretty safe” from them. If they want to sue you, they will, and could bankrupt you with the legal fees alone.
Reusing branding always opens you up to liability. There are a lot of angles that you wouldn't expect, that trademark can be used to attack you with. And Nintendo are very hostile to any and all uses.
While Nintendo might not lose the trademark entirely if they don't sue, they could risk weakening its strength, therefore they have to sue in this case.
Consistent inaction against infringers can lead to the public perceiving the trademark as less distinctive. This can make it harder to protect the trademark in the future, and can encouraging further infringement.
It appears that they're gathering orders for to do a group-buy of a custom-machined aluminum shell for the keychain widget, and that this newly-minted custom-machined hunk of aluminum includes the a replication of the Nintendo logo.
That's commerce.
Now, obviously: Their target market knows exactly what they're buying, and they aren't going to be confused by any of this at all.
But trademark law (and the surrounding case law) may not see it that way.
It's easier (and a lot less fear-inducing) to cease-and-desist before Nintendo's IP lawyers send a nastygram than it is to do so afterward. (And in order to keep their trademark intact, they pretty much have to send that nastygram. Trademarks are very much a defend-it-or-lose-it thing.)
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"Sorry guys, the first order had to be scrapped along with all of the money we collected and spent on it. If anyone is still interested, the price is still $55 for a shell without the logo if we can get another 30 orders in again."
Using a brand name like this just makes things easier when Nintendo attorneys barely have to roll out of bed when sending a cease and desist order.
Just call it Kawaii and stay slightly under the radar. Sadly, Nintendo will probably come for you anyways.