Mon and the shop 文
The only currency, earned only by studying. What it buys, and what it is never allowed to buy.
There is one currency, 文 mon, and one way to get it: study. It cannot be bought. There is no second premium currency, no exchange rate, and no bundle - the design that exists in most apps specifically so you cannot tell what anything costs.
Mon is the real coin of the period: the 寛永通宝 Kanei tsuho, round, with a square hole so a thousand of them could be carried on a cord. It is also the fifty-ninth character in your own deck, so the number in the band is a word you are on your way to being able to read.
How it is earned
2 mon for every correct answer. 15 for every step of the seasonal track. And a purse at each station you reach on your road, larger for the places that are worth arriving at.
That is the entire list. No daily login bonus, no reward for watching anything, no wheel to spin. The money follows the work, which keeps the number honest - a large balance means you studied a lot, and it cannot mean anything else.
What it buys
Cosmetics, and only cosmetics. The stall 屋台 street stall rotates its stock daily and sells things for your companion to wear and carry. Rarity (common, uncommon, rare, epic, legendary) describes how ornate a thing is, not how much it helps you. None of it touches a card, a schedule or a level.
Mon also buys ascension: taking an item you already own and remaking it in a finer material. The same silhouette has five destinies, 木 鋼 白金 妖 神, and each step up costs more than the last, from 60 to 1,800.
Ascension is where a long balance goes, and it is deliberately the opposite of a gamble: you know exactly what you are buying, exactly what it will look like, and exactly what it costs before you spend anything.
What a mon was worth
The prices here are the prices a traveler on the Tokaido would have recognised. A public bath cost about ten mon, a bowl of soba sixteen, a night at an inn two to three hundred. A gold 小判 koban was four thousand. So 2 mon a card is a bowl of soba every eight answers, and the last step of ascension, at 1,800, is about six nights under a roof.
That is an anchor, not an exchange rate. It is here because a number means more when you know what it used to buy.
What it never buys
Not a kanji, not a reading, not a meaning, not a mnemonic. Not a level, not a rank, not a place on the board. Not a repaired streak. Not a shortcut through a review.
And nothing random is ever sold for money - not here and not anywhere in EdoQuest. The stall deals in earned mon, and where randomness exists it exists only on that side of the line.