Betaori

A player in betaori 「ベタ降り」 ("folding" in English) aims to minimize the chance of dealing into other players' hands, often giving up the chance to win in the process. While a player in betaori can still lose points to tsumo and tenpai settlements, more points will be lost by dealing in.

Overview

Main article: Defense

When playing betaori, you should discard the safest tiles first. This means discarding genbutsu (100% safe tiles) before "relatively" safe tiles like suji and honors, even if it would break a group or pair. Defense is often done against a single player, such as a player who declared riichi, but there are many cases where defending against multiple players is required.

Safe tiles

Determining safe tiles requires deduction from visible tiles, including all discards, dora indicator, and the tiles in the player's own hand. Of course, it also requires the player's active decision to defend (as opposed to continuing to push the hand towards tenpai).

The following is a rough order of tile safety, from most safe to least:

Tile	Description
Genbutsu	Genbutsu are tiles that are 100% safe due to furiten. Any tile a player discards is 100% safe against that exact player. After a player declares riichi, any tile anyone discards without a ron is 100% safe against the riichi-declarer. When the player to your left discards, that tile is 100% safe against every player for that turn only.
Honors (3 to 4 visible)	Excluding kokushi, an opponent needs a copy of an honor to wait on it. Therefore, when 3 or 4 copies are visible, an opponent is less likely to have/wait on that honor.
Kabe	When all four copies of a tile are visible, the same suit tiles towards the outside become safer kabe tiles. For example, if four 3-pin are visible, 1-pin and 2-pin are kabe tiles. This is because it's impossible for any opponent to form a 123 or 234 sequence, so a sequence wait on 1 or 2 is impossible. Tles towards the outside are generally safer.
Suji	When a tile is genbutsu, the same suit tiles 3-away are safer suji tiles. This is because the most common type of wait (ryanmen wait) wins off of tiles that are 3-apart, meaning that suji protects from that. Suji is about as safe as kabe (kabe is a bit safer). Tiles towards the outside are generally safer. Note that 4/5/6 tiles are extra dangerous, so in order to be "full" suji, they require both 3-away tiles to be genbutsu.
Honors (2 visible)	Excluding kokushi, an opponent needs a copy of an honor to wait on it. Safer when at least 1 of the tiles was discarded. Overall, about as safe as suji and kabe.
Sotogawa	When an opponent discards a tile early, they are less likely to wait on tiles towards the outside. For example, is 3-pin is discarded early, it's less likely for them to wait on 1-pin or 2-pin. This is because it's rare for an opponent to discard 3 from shapes like "233", "334", or "133", making a "23" or "34" in hand less likely.
One chance kabe	When 3 copies of a tile are visible, the tiles towards the outside are safer. This works like kabe, but less safe. Decently safe in the early/mid-game, but dangerous in the late-game.
Regular tiles	Regular tiles are quite dangerous. The safest regular tiles will be honors and terminals, but even terminals have a decently high deal-in rate (around 8% mid-game, 10% late-game, 15% on the last turn).

When tiles are equally safe

If two tiles are equally safe, try to discard tiles that are more likely to be dangerous against the other players. For example, if both 6-pin and 1-pin are safe against a riichi player, discard 6-pin first. That way, if another player enters tenpai, the 1-pin in hand will be less dangerous.

If two tiles are still equally safe, it is best to discard a tile that does not reduce hand progress. After all, you can prevent opponents from winning by winning yourself.

Defending against 2+ players

Defending against two players is tricky, since defensive techniques like genbutsu and suji apply to each player individually.

Try to find genbutsu against 1 player (preferably the player who you want to deal into the least, e.g., the dealer), and of the tiles genbutsu against that player, find the tile safest against the other player. After a few turns, riichi furiten / temporary furiten should help generate tiles safe against both players.

Mawashi uchi

Mawashi uchi 「回し打ち」 is a strategy distinct to betaori. A "halfway" style, it aims to retain 1-shanten while discarding relatively safe tiles (e.g., suji, sotogawa tiles). A player undergoing mawashi will discard relatively safe tiles, even at the cost of tile acceptance.

When undergoing mawashi, you should constantly evaluate if you should be folding. If a dangerous tile is drawn and can't be used in the hand, mawashi will often convert to betaori (or sometimes convert to full pushing). If it gets too late in the round, it may also be good to fold, as it is easier to deal in when late in the round. Conversely, if you hit tenpai in a reasonable timeframe, pushing is generally good.

Because mawashi requires good push/fold judgement, it is recommended to learn how to betaori properly before mawashi (new players may discard recklessly, claiming it is "mawashi").

External links

• Basic Defense Techniques in Mahjong

Written work on defense in Osamuko