Short answers, pulled from the story.
The katakana script was developed in the 9th century during the early Heian period. Buddhist monks in Nara created the system to transliterate complex Sanskrit and Chinese texts into Japanese.
The word katakana literally means fragmentary kana. It was formed when monks took the left side of the kanji character 利 and stripped it down to create the symbol カ.
The katakana syllabary includes 48 characters arranged in a 5x10 grid known as the gojūon. This arrangement mirrors the vowel and consonant order of Sanskrit practice.
The katakana script was added to the Unicode Standard in October 1991. The full-width block U+30A0 30FF was established at that time with half-width equivalents encoded later.
Japanese linguists use the katakana script to write the Ainu language by representing the consonant at the end of a syllable with a small version of a katakana. This system includes three handakuten modified katakana such as セヴ and ツヴ to represent sounds unique to Ainu.