Hiragana and Katakana are two 46 character phonetic sets used in Japan. Both composed of the same base phonics, hiragana is used when writing native Japanese words and Katakana is used for foreign words. This rule isn’t always followed though, especially when it comes to advertising.
Take this poster for example, this is for a hot-drink sale, the main title reads “Hotto hotto seeru” (Hot hot sale). The word “hot” is a borrow-word from english, so here we see it written first in Katakana as ホット and then strangely in hiragana as ほっと.
Here’s another, but in reverse. This is a promotion for train trips to go and enjoy winter crab. So the japanese word for crab is kani(かに) which is featured on the main title, but right next to it the word is repeated in katakana as カニ – which admittedly looks much more similar than the previous example.
The only reason I can think of for this is the Japanese character sets lack an upper or lower case, and using bespoke fonts can make the characters a nightmare to read, so replicating in the other character set for effect kind of fulfills that. Especially Katakana with its simplified, angular form.
I’m not really going anywhere with this, it’s just something I find interesting