I have two Japanese player collections, and Rami-chan is one of them. So while this post is basically focusing on the release, the cards are heading to the player collection!
On April 4, 2017, Hits released a set of eight "Trading Mini Color Paper" cards. Actually, it's a set of 16, featuring eight players including manager Alex Ramirez. Cards with an N- prefix are normal cards, while SP cards are short printed, though there's no published ratio.
Version 1.4 reprinted the first eight cards and added four additional players, bringing the checklist to 12. Of course, that does mean that there are really 24 cards to be found. It does appear that all of the players have some authentically signed versions as well, but there is very little information about that on their website.
Version 1.4 boxes include 10 cards - six from the first "series" and four from the second "series". This essentially means that you will get one full second series in each box, though with SPs this might not be true. Likewise, it might be safe to assume that the first series boxes contained 10 cards, and thus most likely had a full set.
Each pack - one card - costs 500 yen. The secondary market has provided some of these cards less than their original price, but the lowest I've seen of any card from this type of release is about 300 yen, for Carp singles from a couple years ago.
These are blank-backed; actually, they have yellowish backs and the foil border folds over to the back. There are flecks of silver foil also embedded in the paper.
The design of the card itself - the square, hard board with foil edges and foil-embedded paper, called shikishi - is copied from the design of congratulatory boards and autograph boards commonly found across Japan. The fancy "paper" is used for friends and coworkers to write special messages most commonly for farewell parties, but also can be used for birthdays and other special events. While the plain, solid-colored versions are the most traditional, themed versions can be found, like round ones printed to look like sports balls.
The regular ones are pretty large, too - about 9.5" x 10.75". Sometimes I come across autographs on these boards, and I like them as they'll mount well or sit solidly on a shelf. While "fine" artists don't necessarily like them because they're mounted on a stiff board, they're great for autographs and sketches, in addition to farewell or congratulatory messages.
So there you go, a little bit of Japanese culture mixed in with a trading card post.