(bought the game, reading now)
Eh. Author said inspired by (clearly L5R); so being at least a little culturally out of touch kinda comes with that territory (yeah I loved L5R back in the day, but it did have its "yeeeeshh" moments). It's not a bad take on the genre, though!
And the system seems fine. It's clearly focusing on 1 on 1 samurai duels. The rules seem pretty tight actually. Looks like most swordfights would take a while though given the damage track (similar to L5R)... but the manuvers and stuff seem inspired. All in all, a solid rules-focused take on fantasy samurai fights.
But indeed the Japanese use is a little Fingernails-on-Chalkboard. The biggest slap in the face is the combination of Chinese and Japanese in "Zhou Shima" (the setting name) (is it supposed to be like 周, like the Zhou Dynasty of China? Why is it half Chinese and half Japanese???).
And of course, right on the cover, is (in Japanese quasi-katakana) "Rohhl Plain Turtle". That got a laugh on Japanese TRPG Twitter. It's 100% okay not to know Japanese and write a game loosely based on Japan! Language and design are totally two different things, and it would be foolish to say that someone inspired to write a game about Culture X must master Culture X's language or anything like that.
...But in that case, maybe go on reddit/twitter or something and ask, when you plan to make up Japanese-sounding names or write in Japanese. Folks will chime in for free if it's just a word or two.
BTW, RPG in Katakana would be ロールプレイングゲーム