I looked into it and I think I may have the answer. Knew it wasn't similar in Japanese (crab = kani), so that wasn't it. Then I assumed it was her astrological sign, since Japan loves that shit, but she's an Aries.
So then I thought it was just the artist, as they're all from the same guy, and that seems to be the answer. The Google Translate of the description from this picture says "Koume I want to do my best until that it's like unrivaled crab become an official set." which is pretty broken, but seems to imply "I want to make tons of these crab pictures until it becomes an official thing."https://www.pixiv.net/member_illust.php?mode=medium&illust_id=27334346
So there it is. Probably. Unless that Google Translate is completely wrong or implies the wrong meaning.