So, I've been trying to figure out the hopefully non-random Inkling alphabet. Most of my ideas & leads so far have proved fruitless.
I compiled this image of the squid girl amiibo box – the Japanese and English versions – and then an in-game picture of it, which seems to be based on the Japanese version.
Looking at the "GEAR GET!" part on the right, some notes:
• The o-with-a-hook character ends the top word and begins the last.
• The "LI" seems to be a single character, and appears in both the top and bottom word.
• The "Иㅏ" appears both in the top word and the left text blurb/speech bubble (last word on first line).
It'd be pretty crazy (i.e. dumb) if words weren't all consistently left-to-right or right-to-left, so I'm assuming it's one of those (probably left-to-right like English and [non-Classical] Japanese).
Not really sure if this image helps or anything, or if it can be "solved" – it may just show the alphabet/writing system is completely arbitrary/random, unfortunately. If anyone has ideas, please feel free to help out.
Attached to this post is my (non-exhaustive) compilation of the in-game brands with their English and Japanese names, along with a couple miscellaneous pictures of translated or maybe-translated text.
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EDIT: There's a reddit thread discussing/analyzing this image as well that I just stumbled across:
http://www.reddit.com/r/splatoon/comments/38lge0/the_inkling_language_may_sadly_just_be_gibberish/