That's right. They are all Japanese things in increasing order of deadliness.
With that said I'm not sure how squid managed to be more dangerous than a kappa. >Kappa are usually seen as mischievous troublemakers. Their pranks range from the relatively innocent, such as loudly passing gas or looking up women's kimonos, to the malevolent, such as drowning people and animals, kidnapping children, and raping women
~wikipedia
The best gift is cucumber, which the Kappa can't resist. Don't go swimming in Japan after eating cucumber, because they will drown you when they smell it on you.