The idea is not bad, and the implementation seems solid for a first draft.
I noticed via the sample that you’re taking a KaniWani approach, that is, testing your recall of the Japanese word when prompted by the English one.
If your goal is simply to add in some supplemental studying, then this seems fine, but just be aware that it’s practicing something fundamentally different than WaniKani, and so your results may vary.
You’re also going to have issues once you have multiple words that have the same primary meaning—doubly so if they are in the same review queue. For example, 理由 (7) vs 理性 (14) vs 故 (26) vs 訳 (32).
Perhaps you could do something like a “spelling bee” approach, by grabbing one of the context sentences along with the word. It might drastically increase the time needed, but it might help differentiate the synonyms or homophones. And you could then also consider making it so that you could either do it EN → JP or JP → EN. I would find myself a lot more interested in something that did this (particularly with the prompt being the Japanese word & sentence).
Also, if you wanted considerations for what you could remove to trim down the total time slightly, it might not be desirable/necessary for some people to have the item number mentioned at the beginning of each one, as long as there’s something else that sufficiently separates the items, like the pause or maybe a short tone or something.
Anyway, those are just my first thoughts. Certainly an interesting idea, though I don’t know if I’d find myself using it at this point.