On the Language of KNK
Raiko is very obviously a world rooted very strongly in the Japanese Sengoku. Consequently, they are speaking Japanese - but not modern Japanese. The language of the time was Late Middle Japanese, which, much like Late Middle English, is legible to modern speakers, if strongly dated (imagine reading Chaucer, or Shakespeare - you understand the words, but there's a lot of figurative parsing and legwork you have to do to really understand the entirety of what's being conveyed).
Why do I care about a language im not writing in? well I am using a lot of jpn for authenticity, so you need a guide. and also language informs how people communicate and think and i want to get into these characters' pores because im insane.
Personal Pronouns
different from the ones you are familiar with! here is a table of them! including second person!
Honorifics and Forms of Address
keigo vs familiar/informal speech, the differing situational ways people address each other, heres another helpful list
Kanji and Kana
kanji's origin in the Chinese writing system, kun vs on-yomi readings, kana and its history, how things are named
Glossary of Kanji
literal kanji and kana glossary of character and place names