This is a bit about what I've heard and remembered about the Shuku Keitai Kaitsu Tamagotchi Plus (Keitama).
Some parts may not be correct because this is just from memory. Also I was looking at a scan of the Keitama's manual a while ago which is in Japanese, and I can't read Japanese too well.
As far as I know this Tamagotchi can exchange passwords with an application that can be downloaded onto Japanese mobile phones. (I'm not totally sure though- this is probably incorrect due to my rubbish knowledge of Japanese.) Think of it as a kind of replacement for v3 Tamatown.
There are three games- a get-the-notes game like the v3, basketball (a game of timing I think) and a race game (guess which place your Tamagotchi will come).
I think you can donate Gotchi Points to the King on this version, I seem to remember someone saying that if you donate 1 000G, then a Super Unchikun or something like that will clean up your Tamagotchi's messes for you.
The Keitama can communicate with other Keitama, as well as the original Tamagotchi Plus (and possibly other Tamagotchi Connexion versions from v1-v4.5), the Deka Tamagotchi and mobile phones (I think it's just exchanging passwords though).
There's a way to stop your Tamagotchi dying on this version but it only works if you catch your Tamagotchi while it's dying and if you already have had a Tamagotchi die on you. If you see your Tamagotchi dying, you can go and visit one of the already deceased Tamagotchi's graves and the spirit may come and save your Tamagotchi.
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