I do this with my kids' "exam review" materials. I'll take a photo of the pages marked "study this for test" and send to Gemini and say "make a test out of this" and it'll create an exam with questions, answers, multiple choice, true/false, fill in the blank, etc.
It's really impressive. So I just tried it to do what you were asking:
> Give me the first three paragraphs of Genji Monogatari in Japanese (I've only done this for an initial seed text; you'd probably instead use your own source text)
Here are the first three paragraphs of Genji Monogatari (源氏物語) in Japanese:
いづれの御時にか、[snip]
> Create spaced learning repetition of those three paragraphs using cloze detection for any word that is not in the top 5000 most common Japanese words
Okay, I can help you create a spaced repetition exercise for those three paragraphs from Genji Monogatari. This will use cloze deletion (fill-in-the-blanks) for words that are generally less common in modern Japanese or are characteristic of classical Japanese. Since I don't have a real-time tool to check against a specific "top 5000 words" list, I'll select words based on common knowledge of Japanese vocabulary and classical forms that would typically be targeted for study.
Please note that the third paragraph you provided contained "тревоしき", which appears to be a transcription error. [This is true. Gemini's first three paras of this novel did contain this transcription error.] I will substitute it with "あさましき" (asamashiki), meaning "shocking" or "deplorable," which fits the context of referencing Yang Guifei and potential societal disruption. If you believe another word was intended, let me know!
What I received was a canvas I can export to Docs, and it begins with:
Genji Monogatari - Spaced Repetition Cloze Exercise
This exercise is designed to help you learn and recall less common vocabulary and classical expressions from the beginning of Genji Monogatari.
Paragraph 1 - Cloze Test
いづれの ______ にか、______ 、______ あまた ______ たまひけるなかに、いと ______ き際にはあらぬが、すぐれて ______ たまふあり ______ 。はじめより我はと ______ たまへる ______ 、______ ものに ______ そねみたまふ。同じほど、それより ______ の更衣たちは、ましてやすからず。
Paragraph 1 - Answer Key
いづれの 御時（おんとき）にか、女御（にょうご）、更衣（こうい）あまた さぶらひたまひけるなかに、いと やむごとなき（やんごとなき）際にはあらぬが、すぐれて 時めき（ときめき）たまふありけり。はじめより我はと 思ひあがり（おもいあがり）たまへる 御方々（おんかたがた）、めざましきものに おとしめ そねみたまふ。同じほど、それより 下﨟（げろう）の更衣たちは、ましてやすからず。
Paragraph 1 - Vocabulary
御時 (おんとき): reign, era (honorific)
女御 (にょうご): Imperial consort of high rank
更衣 (こうい): Imperial consort of lower rank than Nyōgo
あまた (amata): many, much (classical)
さぶらひ (saburahi): (archaic form of 侍う - saburau) to serve, to be in attendance (humble)
やむごとなき (yamugotonaki/yangotonaki): exalted, of very high rank, distinguished (classical)
[it continues the same way with para 2, 3]