Stage 4 (Oicho-Kabu) Development Update

We are currently developing "Oicho-Kabu," the bonus stage for Stage 4.

Oicho-Kabu is a traditional Japanese card game that feels somewhat like a cross between Baccarat and Blackjack, played with Hanafuda cards.

*Since the game only uses the numbers 1 through 10, it can also be played with a standard deck of playing cards.

We have uploaded an unlisted YouTube video showing the current work in progress.

(Note: Audio has not been added yet.)

Basic Rules

The goal is to compare the last digit of the total value of two or three cards.

The Player wins by having a higher number than the Dealer.

There are also several special hands.

Hand Types

There are ten standard hands determined by the last digit of the total card value.

• Buta: 0

• Pin: 1

• Nizo: 2

• Santa: 3

• Yotsuya: 4

• Goke: 5

• Roppo: 6

• Shichiken: 7

• Oicho: 8

• Kabu: 9

In addition to the standard hands, there are also special hands.

Many local variations of Oicho-Kabu exist, but Battle Hanafuda adopts only the three most widely recognized special hands.

• Shippin: 4-1 or 1-4 (Player-only hand)

• Kuppin: 9-1 or 1-9 (Dealer-only hand)

• Arashi: Three cards of the same month (three of a kind)

The ranking of hands, from strongest to weakest, is:

1. Arashi

2. Kuppin

3. Shippin

4. Standard Hands

When both sides have an Arashi, the winner is determined by the value of Month mod 5 (the remainder after dividing the month number by 5).

[c]{4|9} > {3|8} > {2|7} > {1|6} > {5|10}[/c]

*This ranking is based on the level of risk involved in drawing the deciding card.

Please note that this is not an official rule.

Unlike Koi-Koi, which became popular after World War II, Oicho-Kabu is a much older game dating back to the Edo period, and many regional variations developed over time.

Because it was traditionally associated with gambling, rules varied from region to region and even from one gambling house to another. As a result, there is still no universally accepted ruleset today.

Strategy Notes (Using These Rules)

For reference, the statistical appearance rate of Arashi under these rules is approximately 0.24%.

This estimate assumes that whenever a player starts with a pair among the four available fields, they always attempt to complete an Arashi. In practice, the actual rate may be even lower.

In other words, Arashi is not something you can reliably aim for.

Because of this, players can slightly improve their long-term win rate by focusing on the expected value of the other hands.

As the Player, choosing a Pin (1) or Yotsuya (4) field and aiming for Shippin provides a small statistical advantage.

If neither Pin (1) nor Yotsuya (4) is available, choosing the rightmost field provides the most public information when deciding whether to draw a third card. For example, if your current total is 4 and many cards valued 6 through 9 have already appeared, the risk of "busting" and ending up with a lower number becomes slightly smaller.

From an information perspective, the Dealer has the greatest advantage because they make their decision with the most information available.

An Arashi based on Month 4 or Month 9 carries the highest risk of backfiring, so from a purely strategic standpoint it is usually not worth pursuing.

However, if you actually pull it off...

It's incredibly exciting.

Battle Hanafuda-Specific Rules

Oicho-Kabu is an extremely exciting game.

When I was in high school more than twenty years ago, it became wildly popular among my classmates.

After school, classrooms would echo with dramatic declarations like:

"One more card!"

or

"ARASHI!"

delivered with all the intensity of a Kabuki stage performance.

We even used mechanical pencil leads as betting chips. At one point, demand became so high that the school store and nearby stationery shops occasionally ran short of mechanical pencil lead refills.

People naturally become excited by games where chance determines victory and defeat.

The version of Oicho-Kabu in Battle Hanafuda is being designed around a different challenge:

"How much of that excitement can be preserved after removing every element of gambling, including virtual gambling?"

I would like to recreate the excitement I experienced back then in a digital game.

However, under those conditions, it is not an easy task.

The following rules are not finalized yet, but they represent the current concept for Battle Hanafuda's version of Oicho-Kabu.

Core Rules

• Play as the Player side at all times.

• Up to three rounds can be played.

• Winning a round grants a reward and doubles the stake for the next round.

• A draw preserves the current stake and advances to the next round.

• Losing a round immediately ends the game.

• The initial stake for Round 1 is determined by the amount of money the player has when reaching Stage 4.

Stake Growth

Rewards and stake increases depend on the winning hand.

Initial Stake

The initial stake for Round 1 depends on how much money the player has upon reaching Stage 4.

The thresholds are still under consideration, but one possible setup is:

• Less than 50y: rate = 10y

• 50y to less than 100y: rate = 20y

• 100y or more: rate = 35y

Theoretical Maximum

Under this system, the theoretical maximum stake progression is:

• Round 1 = 35

• Round 2 = 140

• Round 3 = 560

The theoretical maximum reward is 2,240 (560 × 4), although any value above 999 will be capped at 999.

Schedule Adjustment

Originally, we planned to release a major update immediately after Oicho-Kabu was completed.

However, development progressed faster than expected, so we decided to adjust the schedule and instead release a larger update after all remaining Arcade Mode content (Stages 4–8) has been completed.

At the moment, the music for the later stages is still unfinished, so our short-term plan is to continue releasing smaller updates, such as adding more tracks to Music Room.

Why Adjust the Schedule?

This idea is not finalized yet, but after Arcade Mode is complete, I have been considering creating a separate Rogue Mode inspired by deck-building roguelikes, using Hanafuda cards.

Steam recently held a Deckbuilders Fest, and participation in events like that could provide additional opportunities to reach new players. If the player base grows, it may help us achieve one of our long-term goals: stable online matchmaking for multiplayer games.

Of course, I understand that it is not that simple.

That possibility is one of the reasons we decided to preserve opportunities for future major updates while continuing development.