Board Game Arena

There are serious problems in current koi-koi rules. Rules applied currently isn't correct and needs to be changed.
These rules are original Japanese rules, and is omitted in the BGA koi-koi rule.

1. After a player announces koi, he will win the points unless opponent develops yaku. Even though a player didn't make any points after koi, he still wins the game. However, in the BGA rule, no one gets any points if this happens.
2. Yaku which needs sake cup('viewing the moon', 'viewing the cherry blossoms', and 'viewing the blossoms under the moon') breaks when any willow card is captured, since the rain(willow represents rainy day, and those set are called 'ame(rain)' in Japanese) will ruin the party. This rule is not currently applied in the BGA koi-koi(However, a player who made yaku with sake cup needs only 1pt regardless of the ruined party. For instance, a player who built 'viewing the moon', and announced koi, he can win the game if he captured 11 plain cards, regardless of broken 'viewing the moon' yaku by willow cards. In this case, he will win the game with 2pts)

These rules must be put into consideration, and the BGA koi-koi rule needs to be changed.

Thanks for taking the time to post about this. This information is really interesting.

1. Both rules I have used for reference state the opposite: "If the players both use up all the cards in their hand, the game is declared a draw. No score is awarded to anyone, even if someone has a yaku combination melded (had previously said "koi-koi")". I also tried to look at the Nintendo rules (https://www.nintendo.co.jp/n09/hana-kabu_games/) with Google Translate and didn't find anything about this.

It is my understanding that there is a lot of regional variants for Hanafuda games. Might this be such a variant ? Do you have a rules reference mentioning this rule accessible on the internet?

2. I love this rule. I think it makes the game more strategic by making the sake cup less powerful. But this is the first time I hear about it, it was not mentioned on any of the Koi-koi websites I visited.

Maybe also a regional variant? I think I'll implement this as an option when creating the game. A reference link to a website writing about this rule would also be very helpful if you know of one.

Though "viewing the blossoms under the moon" is cancelled, but actually it's worth "10" koban now. In other words, the points of "2 bright cards+ 1 special animal card" are equal with "Five Bright". Since there's a repeated cup card, it shouldn't double counted Viewing the Moon & Cherry Blossoms.

I suggest "viewing the blossoms under the moon" should be independently counted as 6~7 koban(exclude Viewing the Moon/Cherry Blossoms), it's more reasonable.