Mushi [虫 - むし, lit. “Insect”] is a 2-player hanafuda game played either with a 40-card Mushi-bana deck, which lacks the 
Peony and 
Bush Clover suits, or a standard deck with those suits simply removed. Some of its characteristic features are the use of the 
Lightning card as a wild card, relatively few yaku, and zero-sum scoring.
¶ Setup
Game setup involves choosing a dealer [親 - おや, oya], shuffling the deck, and distributing the initial cards. A decision must also be made as to how long the game will last - common options are 6 rounds, 12 rounds, or until some target score has been met by one player. Any other house rules should also be established at this point in order to keep gameplay smooth and fair.
¶ Choosing the Dealer
There is no required method for selecting who is the first dealer, though a typical method in hanafuda games is to shuffle the deck and have both players draw one card each. The player who drew a suit for the earliest month becomes the dealer. If both players drew from the same suit, the player drawing the higher point card becomes the dealer. In cases where there is a tie, this process can be repeated.
¶ Distributing the Initial Cards
Eight cards are distributed to each player, and eight to the table. While there is no required method for this distribution, it is common for the dealer to give four to their opponent, four to the table, four to themself, and then repeat.
The remainder of the deck is placed face-down to form the draw pile.
If 4 cards of the same suit are dealt to the field at the beginning of a round, generally a misdeal is declared and the same dealer shuffles and distributes cards once more.
Whether or not a misdeal is declared when 4 pairs of different suits are dealt to the field is optional; be sure to agree on this as a house rule before play begins.
Whether or not a misdeal is declared when the Rainman, the Swallow, and the Willow Ribbon are all dealt to the field is not something the available rulesets care to mention, although it seems likely that it is treated as a misdeal since none of those cards can be captured in this case.
¶ Gameplay
Each round, the dealer is the first to play, and turn to play alternates. The turn structure of Mushi is entirely typical of Hana-Awase-derived games such as Koi-Koi.
¶ Turns
On their turn, a player chooses a single card from their hand and plays it to the table.
- If it belongs to the same month as another card on the table, then the cards match, and this matching pair is moved to the player’s score pile.
- If the played card matches with two cards on the table, then the player may choose which one they capture.
- If the played card matches three cards on the table, then all three are captured along with the played card (this is to prevent cards from becoming ‘stuck’ on the table and unable to be captured). To help in recognising this case, three cards of the same month on the table are often collected into a small pile at the beginning of the round.
- If the played card does not match any card, then it remains on the table, and may subsequently be captured by other played cards.
If a card is played that matches something on the table, then the player must capture, as described above. However, there is no obligation to play a card that matches something, even if the player has one in their hand; they may, if they wish, elect to play a card that matches nothing on the table.
As is typical of hanafuda games, each player’s score pile should be kept face-up and laid out on the table, so that its contents are fully visible to all players. Ideally, the cards should also be arranged by type (Brights, Animals, Ribbons, and Chaff) to make detecting yaku easier.
After a card has been played from their hand, the player takes the top card of the draw pile, turns it face-up, and immediately plays it to the table in the same fashion.
After both cards have been played- one from the player’s hand, and one from the draw pile- the turn ends, and the next player takes their turn.
¶ Wild Card
In Mushi, the Lightning card serves as a wild card, and can be used to capture any other individual card except another Willow.
If it is on the field, it must be captured by the first non-Willow card drawn from the deck.
If it is dealt on a player’s hand, that player may use it to capture a non-Willow card during any of their turns.
If it is drawn from the deck, it must capture a non-Willow card on the field.. If there are no non-Willow cards on the field, then it is discarded onto the field, to be captured later.
If, however, the Lightning card is the last to be drawn from the deck, it captures all remaining cards in play.
¶ End of Round
The current round ends when both players have played 8 turns and thus exhausted their hands. Due to the reduced size of the deck, this will also coincide with the draw pile being emptied.
Due to the usage of a wild card, most rounds will end with two unpaired cards - one Willow, and one that matches the suit of whatever card was captured by the Lightning.
In this case, the last Willow will be added to the scoring area of the player who captured the other two non-wild Willows, and the remaining card is added to the scoring area of the player who used the Lightning to capture its mate.
At this point, both players tally their scores for the round, as described below. The player with the highest score becomes the dealer for the next round.
What happens in the (unlikely) event of a tie here is not something the available rulesets care to mention, although it seems likely that the current dealer remains the dealer for the next round, as in Koi-Koi.
¶ Scoring
At the end of the round, players score both for the value of their captured cards, and for any yaku (scoring combinations) they managed to collect in their score piles.
The values of each card in Mushi are the standard ones used in Hachi-Hachi and many other games, though the reduction in suits leads to different distributions of those card types.
| Card Type | Value | Number in Deck |
|---|---|---|
| Bright | 20 | 5 |
| Animal | 10 | 7 |
| Ribbon | 5 | 8 |
| Chaff | 1 | 20 |
This means that the total value of the entire deck is 230. Since each player could conceivably capture exactly 115 points, only the points in excess of that are counted. Hence, to calculate one’s initial score for a given round, add up the points for all cards captured, and subtract 115.
Then, the players check for any yaku they formed. The total value of a player’s yaku is paid to them by their opponent, in a zero-sum fashion. For example, if a player has 40 points’ worth of yaku, then they gain 40 points, while their opponent loses 40 points.
In summary, the total amount of points won or lost by the players at the end of each round is
Player's Score = (Player's Total Card Points - 115) + Total Value of Player's Yaku - Total Value of Opponent's Yaku.
At any given point, the scores of both players should sum to zero.
¶ Yaku
There are typically only 4 yaku used in Mushi. Players earn points for each of these that they capture, and subtract the same number of points from their opponents’ score. Some variants only have 3 yaku, excluding “Five Brights”.
There are no mutually exclusive yaku here; players score for every yaku they possess!
| Value | Name of Yaku | Composition |
|---|---|---|
| 30 | Five Brights 五光 [ごうこ, gōko] |
     |
| 25 | Three Brights 三光 [さんこ, sanko] |
 Not to be confused with the yaku of the same name in Koi-Koi; this one includes the  Bush Warbler as a pseudo-Bright. |
| 10 | Four Wisterias 藤シマ [ふじしま, fujishima] |
All 4  Wisteria cards.    |
| 10 | Four Paulownias 桐シマ [きりしま, kirishima] |
All 4  Paulownia cards.   |
¶ Scoring Example
If Player A captured 2 Brights, 3 Animals, 3 Ribbons, and 10 Chaff, and made the “Three Brights” yaku, while Player B captured the rest of the cards in the deck and made the “Four Wisterias” yaku, Player A would calculate their score as 2(20) + 3(10) + 3(5) +10(1) - 115 + 25 - 10 = (-5). Player B’s score for the round would thus be 5, as the sum of scores in a given round always equals 0.
¶ External resources
📺 “How to play Mushi”, YouTube tutorial by suryong.
¶ Bibliography
- Duarcain. “Mushi 虫.” Hanafuda Hub!, 21 June 2013, duarcain.blogspot.com/2013/06/mushi.html.
- Johnson, Jason, and Antonietta Fazio-Johnson. “Mushi.” Hanafuda Games, Hanami ed., IndianWolf Studios, 2017, pp. 38–40.
- Shiragiku. “Mushi.” Marguerite, www.marguerite.jp/Nihongo/Games/しらぎく花札/むし.html.
- Tobaku Ni Kansuru Chōsa. vol. 121, Shihōshō Chōsaka, 1927, National Diet Library, dl.ndl.go.jp/info:ndljp/pid/1269696. pp. 64-65.