Advantages and Disadvantages of Riichi
Riichi is an extremely unusual yaku.
It places no shape restrictions on the hand, and it also comes with extra upside in the form of ippatsu and ura-dora.
In practice, it is worth about 1.5 han, while also being the easiest yaku to make in mahjong.
Up to this point, this guide has consistently recommended:
"Do not get too obsessed with yaku. Aim to reach tenpai as quickly as possible."
That is the modern speed-first style of play.
This approach naturally leads to more cheap hands without built-in yaku,
but riichi makes up for that loss in scoring power.
So before going further, let us confirm what riichi really means.
Advantages of Riichi
- It lets you add a yaku very easily.
Figure 1 
Dora
You cannot win in mahjong without a yaku. That is the basic "one-han minimum" rule.
Riichi clears that requirement very easily, because all you have to do is stay closed.
Even with a hand like Figure 1, which already has three dora, you can still only win by tsumo if you do not riichi.
So naturally, you riichi.
- It gives you the possibility of ippatsu and ura-dora.
Even with a cheap hand that has no yaku and no dora, riichi always leaves open the possibility of mangan, depending on luck.
If you tsumo with ippatsu and get even one ura-dora, that is mangan.
And if the ura-dora hits the head, even without ippatsu you can still reach mangan.
In many modern free parlors, ippatsu and ura-dora also carry bonus-chip value, which makes this even bigger.
- It stops opponents from playing freely.
The value of riichi is not only in raising your score.
Once riichi is on the table, everyone usually becomes more cautious.
Players start folding, and some give up hands they otherwise could have won.
That increases your chance of tsumo.
Making your opponents unable to play freely is also one of the strengths of riichi.
A classic example is riichi on a tsumo-only Suuankou hand.
Even if the hand is already valuable enough when won by ron, the point of riichi is to stretch out the hand and increase the chance of tsumo.
- Sometimes announcing tenpai actually helps you aim for ron.
Normally, once you riichi, the winning tiles become harder to come out.
But depending on your discard pond, there are cases where riichi can actually help you win by ron.
Common examples are suji traps and honor-tile waits.
For instance, when waiting in Chiitoitsu on an honor tile of which two copies have already been discarded, the so-called "hell wait," riichi is usually the better choice.
Disadvantages of Riichi
- You must put out a 1000-point stick.
You may think 1000 points is cheap.
But in a situation like South 4 where first place is only 700 points ahead, it is a huge amount.
The moment you put out the riichi stick, you drop to second.
As a result, it can create situations where even if third or fourth place wins afterward, you still finish second.
- By revealing tenpai to the other players, you make ron less likely.
If the table is at all competent, people will not casually cut dangerous tiles into a riichi.
So when you absolutely need to win by ron, damaten is often better.
- After riichi, every draw except a winning tile or a tile you can closed-kan must be tsumogiri.
There is a saying that riichi is "a declaration of violent discards."
Once you riichi, every tile you draw must be discarded immediately unless it wins the hand or can be used for an ankan.
So even if someone has already called 
, if you draw 
after riichi, you still have to cut it.
- You cannot improve the hand afterward.
Draw 
In this example, drawing 1-pin should improve the hand by five han through Junchan and Sanshoku...
But if you have already riichi'd, even that tile must be tsumogiri.
With those strengths and weaknesses in mind, let us now move on to actual riichi decisions.
Original Japanese page: http://beginners.biz/reach/reach01.html