Mahjong Defense and Push-Fold Guide | Genbutsu, Suji, and Kabe

Evaluate each opponent separately

The discards lined up in front of an opponent form that player’s discard area (kawa). When an opponent wins by ron on your discard, you have dealt in (hoju). When defending, first decide whose ron you most want to avoid, then check that player’s discards, called tiles, riichi declaration, and the tiles visible on the table.

Even for the same 1m, you may have evidence that it is safe against the player to your left, different evidence against the player across from you, and none against the player to your right. Safety is not an inherent property of a tile; it depends on the opponent.

When two players declare riichi, a tile safe against one may still deal into the other. If no tile is safe against both, separate your evidence into two columns, such as “personally discarded by the player to the left” and “a candidate based on number patterns against the player across.”

Use the same opponent-specific approach against a player with open melds. Unlike a riichi hand, the wait is not necessarily fixed and may change after the opponent discards a tile from the hand. Visible calls can suggest yaku such as honitsu, yakuhai, or toitoi, but they do not reveal the entire hand. Estimate tile danger separately from the likely value if you deal in.

The same tile already discarded by the target player

The same tile already discarded by the opponent you are watching is called genbutsu. Under the furiten rule, that opponent cannot win by ron on a tile identical to one they have discarded. If you decide to fold completely, look for these tiles first.

Genbutsu only prevents the target player from winning by ron on your discard. It cannot prevent that player from winning by tsumo and does not guarantee safety against anyone else. Even if the player to your left discarded 4m, it will deal into the player across if they are waiting on 4m.

Furiten caused by passing on another player’s discard lasts for different lengths depending on whether you have declared riichi. Under official M.LEAGUE rules, a player who has not declared riichi and passes on a winning tile becomes furiten for the current turn cycle and cannot win by ron until completing their next draw and discard. If a player passes on a winning tile after declaring riichi, furiten lasts until the hand ends; they can no longer win by ron, and only a tsumo win remains valid.

Because a player who has declared riichi cannot change their wait, a tile discarded by another player after the riichi and not claimed by ron remains safe against that riichi player until the hand ends. Under this rule, a tile that passed against a player who has not declared riichi is not guaranteed safe after that player completes their next draw and discard, because their current-turn furiten then ends. Their hand or wait may also change in the meantime. Check the order of discards and whether the opponent has declared riichi.

The order in which you discard genbutsu also matters. If you have several, compare which tiles are likely to remain safe on later turns, which are safe against another attacker, and which least obstruct a possible recovery of your hand. Think one tile ahead instead of discarding every genbutsu immediately.

A clue for narrowing down waits that extend on both sides

With 2m3m, either 1m or 4m completes a sequence. This two-sided shape is called ryanmen. Suji uses the relationship between these ryanmen waits and furiten to rule out specific possibilities.

Number tiles can be grouped into three suji: “1, 4, 7,” “2, 5, 8,” and “3, 6, 9.” If 4m is safe against the player, they cannot ron on 4m with either a 23m wait for 1m or 4m or a 56m wait for 4m or 7m. Therefore, 1m and 7m are less dangerous against these two-sided waits.

However, this does not mean that “if 4m is safe, 1m and 7m are also safe.” A wait for 1m alone, a wait for either 1m or an honor tile, or a wait for the tile between two numbers can still remain. Suji rules out fewer waits than a safe tile does and is not a guarantee.

1-4-7 suji

2-5-8 suji

3-6-9 suji

The reasoning differs between checking both sides from a safe middle tile and checking only one side from a safe edge tile. Even if 1m is safe, a 56m wait for 4m or 7m is still possible, so 4m cannot be considered entirely safe. Do not merely memorize the number sequences; check which two-tile groups are ruled out.

Three waits that suji cannot rule out

A shape waiting for the single tile that will become the pair is called a tanki wait. A shape waiting for either of two pairs to become a triplet is called a shanpon wait, while a shape waiting for the tile between two numbers is called a kanchan wait. Because none of these uses a two-sided structure, suji alone cannot rule them out.

Tanki wait on 1m: 4m being genbutsu does not make 1m safe

Shanpon wait on 1m and East: a wait that does not use a sequence

Kanchan wait on 2p with 1p3p: a safe 5p does not rule it out

Tanki waits, shanpon waits, chiitoitsu, and waits created by rearranging sequences can all fall outside suji. Suji is therefore not a guarantee of safety; it only reduces some ryanmen possibilities. When folding completely, prioritize genbutsu over suji.

Kabe, no-chance, and one-chance

Kabe uses the fact that all four copies of a numbered tile are visible. Count tiles in your hand, discard areas, open melds, and dora indicators. If all four 3m are visible, an opponent cannot hold 2m3m, so 1m cannot complete a ryanmen wait.

When all four copies of a tile needed for a particular ryanmen shape are visible, that possibility is called no-chance. If all four 3m are visible, 1m cannot complete a 1m/4m ryanmen wait using 2m3m. A tanki or shanpon wait on 1m is still possible, so no-chance does not mean absolutely safe.

One-chance is when three of the required tiles are visible. If an opponent has the last unseen tile, they can still form a sequence wait, so this is weaker evidence than no-chance. You also cannot tell whether that unseen tile is in the wall or another player’s hand. It can help you compare options later in the hand when you run out of tiles to discard, but it cannot be treated like a genbutsu.

Kabe differs from suji because tiles in your own hand also count as visible information. For example, three 3m in your hand plus one 3m in a discard area make all four copies visible. Count carefully: to judge 1m, look at the 2m and 3m that an opponent would need for a 2m3m shape, not at the number of visible 1m.

Honor tiles have no ryanmen suji, so be clear about which three tiles “three visible” refers to. If three copies of the same honor tile are already visible outside your hand and you hold the fourth, no opponent can hold any copy of it. That fourth tile cannot deal into a standard tanki wait, chiitoitsu, or a triplet or shanpon wait for a yakuhai. However, it can still be ron’d by kokushi musou, which can wait on that honor tile without holding any copies of it.

If “three visible” includes the honor tile you are about to discard, only two copies are visible outside your hand and one copy remains unaccounted for. An opponent could still have a tanki or chiitoitsu wait, as well as a kokushi musou wait. Always distinguish the total including your discard candidate from tiles already visible outside your hand, and evaluate honor tiles separately from numbered-tile suji.

Six factors for deciding whether to push or fold

So far, the process has been about estimating whether a tile could deal into an opponent’s hand. Next, separately decide whether the potential reward is worth accepting that risk. Check the following six factors in the same order every time.

1. Hand readiness: Check whether you are one tile from a complete hand—tenpai— one step from tenpai—1-shanten— or farther away. If you are in tenpai, also check how many winning tiles remain.
2. Value if you win: Estimate the likely score from your yaku and dora, and add the value of continuing as dealer when applicable. For yaku and scoring, see Riichi Mahjong Yaku Guide and Score calculation guide for details.
3. Stage of the hand: Check the turn count. The later the hand, the fewer draws remain before you can win.
4. Point gap and hands remaining: Check whether it is East 1 or the final hand, and how winning or losing points would affect your placement.
5. Opponent threat: Check whether the opponent has declared riichi or called tiles, whether they are the dealer or a non-dealer, how many players are attacking, and how many dangerous tiles you must discard.
6. Available safe tiles: Estimate how many turns you can survive after folding based on each opponent's genbutsu, kabe, no-chance tiles, and suji.

Thresholds such as “push if the deal-in rate is X%” or “always fold after turn X” do not apply unchanged to every situation. The tradeoff varies with the rules, scores, placement bonuses, red fives, the opponent's hand value, and your wait. Even after pushing, reassess the six factors if another player declares riichi or fewer winning tiles remain.

Three examples where the decision to discard 4m changes

A mangan tenpai with one dangerous tile to discard

Assume 4m is neither genbutsu nor suji against a non-dealer's riichi and could deal in. If you have a mangan tenpai with many winning tiles remaining and can maintain your wait by getting this one tile through, your hand's proximity and value support pushing. Unless the other factors are heavily unfavorable, the decision therefore leans toward pushing.

Two steps from tenpai late in the hand

With the same 4m, the conditions reverse if you are two steps from tenpai late in the hand, must discard several more dangerous tiles, and have safe tiles available. The distance to winning is too great for the turns remaining, so the decision leans toward folding. For a comparison of tile acceptance, see Mahjong Tile Efficiency Guide for details.

Winning in the final hand is required for placement

Even when discarding the same 4m, if you are last in the final hand, winning would improve your placement, and folding would bring the game closer to ending as-is, the score gap supports pushing. Conversely, if you are leading and dealing in with 4m would cost you the lead, avoiding point loss becomes more valuable. Sharing the settlement conditions before play under the scoring rules, including uma and oka, makes it easier to assess the value of each placement.

Estimating waiting tiles and push-fold judgment are not the same problem

Published research has proposed methods for estimating winning tiles from a riichi player's hand composition. Genbutsu, suji, and kabe also provide visible clues for narrowing down possible waits.

However, estimating waits and deciding whether to push or fold are separate problems. To decide whether to push, compare your hand's completion and value, the points you could lose by dealing in, the score gaps, and the number of hands remaining. Reading a tile's danger does not determine whether pushing is worthwhile.

Practice using evidence specific to each opponent

At first, focus on only one opponent and label each tile in your hand as “genbutsu,” “suji,” “four-tile kabe,” or “no supporting evidence.” Before predicting the winning tile, distinguish exactly what each basis supports. Once comfortable, choose a situation in which two opponents have declared riichi, create separate columns for those two players, and look for tiles safe against both.

Next, record difficult hands using six factors: hand progress, expected value, stage of the hand, point differences and hands remaining, the opponent’s threat, and available safe tiles. Do not judge the decision by whether you dealt in; review whether the information available before the discard justified the value you were pursuing.

Over the long term, check not only deal-in rate but also win rate, average placement, first-place rate, and fourth-place rate over the same period. A change may have multiple causes, so form hypotheses by linking the statistics to notes on specific situations.

Common defensive mistakes

• Treating one player’s genbutsu as safe against everyone: Genbutsu is specific to an opponent. Against multiple attackers, look for a tile that is genbutsu to all of them or identify separate evidence for each opponent.
• Treating suji as absolutely safe: Suji rules out only certain ryanmen waits. Tanki, shanpon, kanchan, and other waits remain possible.
• Confusing one-chance with no-chance: If three copies are visible, an opponent may still hold the fourth. The evidence is weaker than when all four copies are visible.
• Forgetting tiles in your own hand: Kabe counts every tile visible to you, including your hand, discard areas, open melds, and dora indicators.
• Pushing merely because you are in tenpai: Also check the remaining winning tiles, hand value, number of dangerous tiles, whether the opponent is dealer, and your placement requirements.
• Assuming you cannot fold after pushing once: A new riichi, another dangerous tile, or fewer winning tiles changes the conditions. Reassess on every turn.
• Choosing a strategy from one result: A dangerous tile that happened not to deal in was still dangerous. Separate the outcome from the information available when you chose it.

Long-term results do not prove a single discard correct

M.LEAGUE Official Results provides several long-term metrics, including average placement, win rate, deal-in rate, riichi rate, and call rate. These show results over a given period from different angles, but none proves that a particular discard was correct. Evaluate each decision by returning to the information available at the time and the six factors.

Separate the basis for safety from the value of pushing

On defense, assess each threatening opponent separately and start with genbutsu. If none are available, use suji, kabe, no-chance, and one-chance while recognizing their limitations. Suji and kabe do not guarantee safety.

For push-fold decisions, check hand progress, value if you win, stage of the hand, point differences and hands remaining, the opponent’s threat, and available safe tiles, in that order. If the conditions change, the correct choice may change even for the same tile.