These notes are all written with the walls closed and hands hidden, just like a live game. I'm writing on the first view, without the benefit of hindsight. This is so that you can judge whether a decision was correct given the information available to you at the time.

http://tenhou.net/0/?log=2015122714gm-000b-11052-9b128c2c&tw=0

E1:
- Basic jihai order is otakaze -> bakaze -> sangenhai -> jikaze. In this case, xia -> pei -> hatsu. Personally I also like discarding isolated terminals before fanpai.
- 9p discard is poor. With the 9s pair, forcing tanyao will likely be slow. Should drop 2s instead to keep the 7p ukeire.
- Well okay you paired 2s, but with four pairs you should be ready for chiitoitsu, so discard 7m or 5p instead of dropping the 9s pair.
- Why discard 2s against that riichi? 2s was completely live. 1p was one chance. Even though he discarded 2p right before riichi, 1p was your safest tile there.

E2:
- Instead of discarding 5m, 2s would've put you in a very wide iishanten.

E3:
- The 35s kanchan had better chances for improvement than 24m, so you should've kept it.
- 788m566s, discarding 7m give you the wider iishanten.
- You've got kind of a weak iishanten for a small hand, and you need to push dangerous tiles to reach tenpai, so you should've folded against that riichi.

E4:
- Jihai order.
- 8s is wider than 3m.
- Why pass up tenpai? You've got two dora and you're dead last. Riichi would've been fine.

S1:
- Discarding 9s instead of 9p would've been a tiny bit better since it's next to the dora.
- Passing up tenpai here isn't too bad, but discarding 2p would be wider than 8m.
- Tanyao nomi? No point in damaten here. Even if your wait isn't great, it's worth declaring riichi immediately just to secure your dealer turn. Even if you don't win the hand, the noten penalties are enough of a benefit, and if you're lucky then they might be worth more than tanyao nomi anyway.

S2:
- On drawing 4s, I'd rather discard 1s instead of 2m.
- When you go full betaori, it's good to discard the most dangerous safe tiles first. For example, toimen discarded 7m, so you should follow up with that before discarding 8s, which is safe against all three players. This helps you to defend better in case other players push against riichi.

S2-1:
- Instead of 5m, discarding 89p would leave you with a better shape, plus tanyao potential.
- Toimen made a third call after riichi, you should assume tenpai and discard xia or 2m instead of 1p.

S3:
- Kokushi from eight tiles? Good luck. You're basically throwing away this hand, and that's going to make the last round much harder for you. Your goal here should be to lower the gap to third as much as you can.
- That said, if you're going to try for kokushi, it's good to discard two suits first to give the impression that it's just honitsu.

S4:
- Your options now are something like dabunan honitsu with a direct hit on third, or riichi tsumo pinfu ittsuu dora or something. Riichi with one dora and a direct hit on first doesn't help you at all.

http://tenhou.net/0/?log=2015122512gm-0029-0000-7d665a48&tw=0

E1:
- Should discard 9m before 1m.
- 8p before 5s.
- Hatsu nomi iishanten, better fold against that riichi. 1m may have been one chance but at that point in the round it wouldn't have been strange for shimocha's 3m discard to have come from 233m. Discarding 2m after that was even more dangerous.

E1-1:
- 1p and 1s might both seem to be isolated terminals, but 1p is a better discard. When it comes to early game tile efficiency, think of 134s as 13s and a single 4s.
- Discarding 2m would be better than 9m, considering the potential for future taatsu.
- 9p gives a much wider iishanten than 3s.
- You've got tanyao two dora for 40/3, which is 7700 as dealer or 11600 by tsumo. You don't need to riichi here.

E1-2:
- Why break up the 9m pair and pass up iishanten? The 45556p shape can easily be improved, and the odds of completing the 468m ryankan are similar to the odds of forming a souzu ryanmen.

E2:
- 5p gives the widest shape, but since it's dora, 3p is the next best choice. Either of these were much wider than 6p.
- Opening up here and discarding 3p locks you into waiting on 8p since 2p is already dead. You've already got a decent lead, you don't need to be so aggressive as to chii a ryanmen.
- Why break up your hand to hang onto the pei?
- Shimocha kept pei as a safe tile. Discarding it indicates that he's either tenpai or iishanten. 3p is one chance but since he discarded 27p there's a 36p aidayonken, so you shouldn't take the risk.
- Discarding 6m against that riichi is super dangerous. Given that 5p was kabe and there were three of both 78p visible, 6p was much safer. And then 8s, why on earth?
- That last 9s was a pointless discard. It's your last draw, there's no way you're going to reach tenpai now, so you should discard the 8s that just passed.

E3:
- Looks like you tilted here. 8s? 3s? Why hold onto the ton? If you're forcing tanyao, why discard 5p instead of 2p? If you're going for sanshoku, why chii 4m? Why then discard 6m instead of 2m?

E4:
- 4p?

S1:
- Discarding 4s practically locks you into waiting on 58m twice, which is relatively weak. Otherwise, you're stuck with an even worse shanpon. Better to keep the 5s ukeire and discard pei instead.
- Toimen discarded 2578m and 35s from his hand. There's a good chance he's waiting on lower pinzu, so discarding 23p is risky, especially after he discarded 1p. Oh, yeah, ron.

S2:
- I'd pon that 4p to go straight to tenpai on 25m.

S3:
- Riichi is a little aggressive here but it's fairly reasonable.

S4:
- Why break up the 12m penchan? Even if you wanted to keep the nan, 8p is a much better choice.
- Okay, tenpai. I'd advise staying damaten in a situation like this. 14s don't look particularly likely to come out, much less against riichi, so you're just exposing yourself to needless danger. Tsumo is enough to win.

Overall, you were pretty lucky in this game. Your tile efficiency could do with some refinement, and you should probably play more defensively. Defense in mahjong isn't just about "not dealing in", it's about minimizing risk at all times.