What is Kokushi Musou? The 13 Orphans Yakuman Explained for Beginners

What is Kokushi Musou?

Kokushi Musou (国士無双), also known as “Thirteen Orphans,” is a yakuman in mahjong where you collect one of each of the 13 terminal and honor tiles (yaochuuhai), with one of them as a pair. It’s the only yakuman that doesn’t form any regular sets (mentsu).

“Kokushi” means an outstanding person, and “musou” means unparalleled - truly a heroic yaku in the mahjong world. With an occurrence rate of about 0.04%, it’s rare, but can be aimed for from your starting hand, making it a romantic yakuman.

Detailed Explanation of Kokushi Musou

Required 13 Types of Terminal/Honor Tiles

List of required tiles:

Conditions for Completion

Kokushi Musou conditions:

1. All 13 terminal/honor tiles

   • Need at least 1 of each
   • 14th tile is for the pair

2. Menzen only

   • No calling allowed
   • No ankan either

3. Special shape

   • No regular sets
   • No sequences or triplets

Usage Examples

Real Game Situations

Example 1: At Tenpai

"Kokushi tenpai!"
"Just need the Green for kokushi"

Example 2: Starting Hand Decisions

"8 yaochuuhai types, can aim for kokushi"
"Deciding between kokushi or normal hand"

Example 3: When Winning

"Kokushi Musou!"
"13-sided wait kokushi!"

Kokushi Musou Shapes

Basic Form (Single Wait)

Tenpai example:

Hand: 1m 9m 1p 9p 1s 9s E S W N Wh Gr R
Wait: Red dragon (tanki wait)

Kokushi Musou 13-Sided Wait

Pure kokushi form:

Hand: 1m 9m 1p 9p 1s 9s E S W N Wh Gr R
Wait: All 13 types above (13-sided wait)

Characteristics:

• Most waits possible
• May be treated as double yakuman
• Ultimate kokushi form

Related Terms

• Yaochuuhai: Terminal and honor tiles
• Yakuman: Highest scoring hands
• Chankan: Kokushi can rob ankan
• Double Yakuman: 13-sided wait treatment
• Kyuushu Kyuuhai: Pre-stage of kokushi

Common Mistakes and Points to Note

Points Beginners Often Mistake

1. Missing Required Tiles

   • Need all 13 types
   • Missing even 1 = invalid

2. Temptation to Call

   • Want to pon honor tiles
   • Calling = no kokushi

3. Ankan Mistake

   • Ankan is also invalid
   • Can only chankan

4. Indecision with Normal Hand

   • Half-hearted is dangerous
   • Early decision is important

Judgment for Aiming at Kokushi

Guidelines from Starting Hand

Criteria for aiming at kokushi:

Relationship with Kyuushu Kyuuhai

Flow decision:

Starting hand with 9+ yaochuuhai types
→ Abort with kyuushu kyuuhai OR continue kokushi

Decision criteria:
- Presence of pairs
- Dora situation
- Point situation

Kokushi Musou Tactics

Early Game Progression

Basic policy:

1. Keep yaochuuhai

   • All are precious
   • Hold second copies too

2. Cut middle tiles

   • 2-8 are unnecessary
   • Cut from edges

3. Don’t be obvious

   • Natural discards
   • Don’t rush

Mid Game Decisions

Continue or switch:

• 10+ types → Continue
• 8-9 types → Watch and see
• 7 or fewer → Consider switching

Handling Dangerous Tiles

Kokushi’s privilege:

1. Everything is safe

   • No furiten concerns
   • Can cut anything

2. High defense

   • Not afraid of opponent’s riichi
   • Offense and defense combined

Kokushi Musou in Practice

Situations Where It Appears

Favorable scenarios:

1. Bad starting hand

   • Scattered hand
   • Many yaochuuhai

2. Early game flow

   • Yaochuuhai gathering
   • Middle tiles not appearing

3. Other players’ moves

   • Signs of flush hands
   • Yaochuuhai being discarded

The Threat of Kokushi

Effect on opponents:

1. Unreadable

   • Can’t judge from discards
   • No safe tiles

2. Can’t defend

   • Even genbutsu is dangerous
   • Complete avoidance impossible

3. Pressure

   • Possibility of kokushi
   • Forces defensive play

Special Rules

Robbing Ankan (Chankan)

Kokushi’s privilege:

Normal: Can't chankan ankan
Kokushi: Can chankan even ankan

Reason: All 13 types needed

Double Yakuman

13-sided wait treatment:

Kokushi Musou Probability

Occurrence Rate Data

Statistics:

• Overall: ~0.04%
• 13-sided wait: ~0.0003%
• Starting hand kokushi: ~0.00003%

Comparison with Other Yakuman

Occurrence rate ranking:

1. Suuankou (~0.05%)
2. Daisangen (~0.04%)
3. Kokushi Musou (~0.04%)
4. Shousuushii (~0.01%)

Mindset for Kokushi

Cautions When Aiming

1. Commit fully

   • Half-hearted is worst
   • Aim until the end

2. Calm judgment

   • Don’t force it
   • Assess the situation

3. Enjoy the chase

   • Pursue the romance
   • Don’t fear the result

Joy of Winning

Value of kokushi musou:

• Memory of a lifetime
• Essence of mahjong
• Topic with friends
• Experience to be proud of

Conclusion

Kokushi Musou (Thirteen Orphans) is a special yakuman where you collect all 13 terminal and honor tiles. Completely different from normal mahjong, as the only yakuman that forms no regular sets, it’s the dream of many mahjong players. Beginners should learn the basics of “collect all 13 types of 1/9/honor tiles,” and if you have 9+ types in your starting hand, actively aim for it. While the occurrence rate is low, the emotion when you achieve it is exceptional. Kokushi Musou symbolizes the depth and romance of mahjong - a wonderful yakuman.