Koi-Koi is a popular card game/rule in Japan played with Hanafuda.
And also the Koi-koi is one of declarations/callings in case a player has formed a yaku in Koi-koi game.
This page explains the rules of "Koi-Koi(こいこい)" which this game has been taken
is popular card game in Japan with "Hanafuda(花札)".
(Hanafuda are playing cards of Japanese origin (karuta cards), used to play a number of games.
Koi-koi is a game for two players at a time.
The goal of the game is to form special card combinations called "Yaku"
from cards accumulated in a point pile.
Determining the dealer is done at first, after that, 12 or 6 times month hands are done.
An initial(*1) dealer (also called the "oya / parent / 親"), is decided upon when the game starts. Each player draws a single card; the player who draws a card from the earliest month(*2) is the dealer of first January hand(*2). If both player's cards are same month, the bigger point one is the oya. If both player's cards are same month and same point(*2), restart the determining the Dealer.
After dealing cards, dealer's turn starts and end, after that opponent's turn starts and end, dealer's turn, opponent's turn, these flow repeats.
8 Cards to each player with face down and the table with face up, though this is done two cards at a time.
The rest of the cards (24 cards) are set aside as a draw pile, and then play begins starting with the dealer.
Player's turn of the dealer or the opponent comes, the player do the following sequence.
On a player's turn, at first he may match by suit
(i.e. month/flower) any one card in his hand with one on the table.
Alternatively, he may discard any one card from his hand face up to the table
(which is his only choice if he can not match anything).
A Player draws one card from the draw pile and places it face up on the playing area.
If this card matches any card now on the table, he must match that card;
otherwise, he must discard it face up to the table.
If matched cards exists by procedures i. and ii. above, a player gains cards in his point piles. Once a yaku(*) has been formed in his point piles, he selects "Koi-koi" or "Stop".
If a player selects "Stop", he gains all the points(*) he is entitled to from the yaku he has,
after that a new hand (next month) begins.