Yasuo is a champion with a unique mana pool known as flow really more known as a shield.He relies heavily on this shield refreshing it constantly using dashes and movement.Known for his late game damage due to building crit for late game damage. Way of the Wanderer

Yasuo is a man of resolve, an agile swordsman who wields the wind itself to cut down his foes. But this once proud warrior has been disgraced by a false accusation and forced into a desperate fight for survival. With the world turned against him, he will do everything in his power to bring the guilty to justice and restore his honor.

Once a brilliant pupil at a renowned Ionian sword school, Yasuo was the only student in a generation to master the legendary wind technique. Many believed he was destined to become a great hero. However, his fate was changed forever when Noxus invaded. Yasuo was charged with guarding an Ionian Elder, but, foolishly believing his blade alone could make the difference, left his post to join the fray. By the time he returned, the Elder had been slain.

Disgraced, Yasuo willingly turned himself in, prepared to pay for his failure with his life. He was shocked, however, to find himself accused not just of dereliction, but of the murder itself. Though confused and racked with guilt, he knew the assassin would go unpunished if he did not act. Yasuo raised his sword against the school and fought his way free, knowing his treason would turn all of Ionia against him. Now truly alone for the first time in his life, he set out to find the Elder's real killer.

Yasuo spent the next several years wandering the land, seeking any clue that might lead him to the murderer. All the while, he was relentlessly hunted by his former allies, continually forced to fight or die. His mission drove him ever forward, until he was tracked down by the one foe he dreaded most – his own brother, Yone.

Bound by a common code of honor, the two warriors bowed and drew their swords. Silently they circled one another under the moonlight. When they finally charged forward, Yone was no match for Yasuo; with a single flash of steel he cut his brother down. Yasuo dropped his weapon and rushed to Yone's side.

Overcome with emotion, he demanded to know how his own kin could think him guilty. Yone spoke: “The Elder was killed by a wind technique. Who else could it be?” Understanding swept over Yasuo as he suddenly realized why he had been accused. He professed his innocence once more and begged his brother's forgiveness. Tears streamed down Yasuo's face as his brother passed in his arms.

Yasuo buried Yone under the rising sun, but could take no time to mourn. Others would be after him before long. His brother's revelation had given Yasuo newfound purpose; he now had the clue that would lead to the true killer. Swearing an oath, he gathered his belongings and, with one last look at Yone's grave, set out with the wind at his back.
The story of a sword is inked in blood.
― Yasuo

I max q first since it's honestly his bread and butter skill.Reduce CD and cast time with attack speed not CDR. Steel Tempest works with Fury reduced by Randuin's Omen and Frozen Heart
Only put points in w when you can actually block a skill from this link also you can block aa attacks.Increases flow gains from sweeping blade good for fast flow bar.Not needed if you can't block anything even for the flow movement as e reduces it's sort of CD and increases damage. Wind Wall
http://forums.euw.leagueoflegends.com/board/showthread.php?t=1519474
Sweeping blade is second to max as it's his source of mobility and can only be used to jump once you have minions to dash to.Good yasuo players will utalize this mobility to poke with q and e in for more damage or to get out.E increases damage every sweep up to 100% four dashes straight. Sweeping Blade
His ultimate is really op in my opinion with huge range and aoe and only requires anyone airborne.increases armor pen which stacks with last whisper making Yasuo basically completely ignore armor.This is the reason armor pen isn't really needed on him unless they stack 1000000 armor.Refreshes steel tempest stacks and flow bar really nice for juking and surviving due to refreshing flow.You honestly don't need to click a target it auto teleports to a target that's airborne when pressing R. Last Breath works with Devastating Strikes
Passive comes with a shield which is OP as you only need to move or dash pretty easy to get.Comes with double the crit chance in replace of 10% crit damage not chance.Pretty straight forward passive not much I need to explain on this since you don't rank passives up.
Way of the Wanderer if you can't really block abilities lane phase against . if you need to block key abilities against such as Mega Inferno Bomb.

You want to farm using your basic attacks early on to not poke if you have these runes and masteries you should try to last hit with a rank one e Sweeping Blade as it deals less damage than your aa when not stacked.Try not to get lucky and crit on minions unless you q and hit the enemy.When your shield is up try to trade with the enemy unless they have a lot more damage you will most likely win since you have a shield Way of the Wanderer which comes fairly quickly.Try to move in between attacks when your shield is gone so you can get your shield faster and dodge skill shots and also stick on the target.if you are pushing lane so you can back try to e q combo and last hit like that as the castor minions should die rather quickly.also note that q can be used to last hit well under tower due to the fact it has more damage and a short CD.you can also combo his abilities when farming aa-q-aa-e should do good damage to both minions and champions.

Pros
Can easily get 100% crit
High mobility Sweeping Blade
Can block tons of things with w including ultimates Wind Wall such as The Culling
High damage
Free armor pen Last Breath
Free shield Way of the Wanderer
Manaless flow
Doesn't really need CDR Steel Tempest Sweeping Blade
Good aa range for melee 175
Q applies on hit effects Steel Tempest
Cons
Q small range Steel Tempest 475
Requires minions to dash Sweeping Blade
Small dash range and small range dashed
Requires some skill with wall Wind Wall
More late game threat due to building crit
Needs to have knocked up target to ult Last Breath
No real sustain other than shield. Way of the Wanderer

Alright a lot of things are very confusing but please bare with me as it is my first time and honestly I don't even know if you guys known how to read the notes because I honestly don't know how to myself.A lot of feedback and maybe some help on how to read my own notes and stuff would really be appreciated please feel free to message me on mobafire if you can I'm not sure or email me at tinp11002@gmail.com

is a very good synergy with a knock up Howling Gale ad shield Eye of the Storm heal Monsoon and passive Tailwind which gives movement speed.
very good engage with Unstoppable Force which can knock up the entire backrow with more precision than and can also peel for you,also he slows enemy attack and movement speed which means less damage and they are slower. Ground Slam Seismic Shard
is a good counter she can jump on you quite easily with Broken Wings Valor and even stun you Ki Burst none is blockable with Wind Wall but Wind Slash even though you have Sweeping Blade.
is a good counter due to attack speed debuff which increases CD and cast time on Steel Tempest with ground slam.Also has a movement speed decrease Seismic Shard which makes flow hard to get which weakens your passive Way of the Wanderer.He also works well with Frozen Heart and Randuin's Omen which increases the attack speed and cast time on Steel Tempest also with Thornmail which reflects damage on aa and Steel Tempest.

On yasuo you need to build Doran's Blade against ap castors where you need to trade and force backs such as against since you can also block skills and aa.You can build Doran's Shield against champions such as who need to use aa especially riven to do good damage early on Runic Blade. Boots against as you can dodge her skill shots easier such as Orb of Deception. Elixer of fortitude and brawler's glove along with Long Sword is more to be ham against champions like since he has almost no damage early game except for maybe Counter Strike.
You want to rush static shiv then go for Blade of the Ruined King against hp tanks like and Bloodthirster against squishy targets like .
Then head for Infinity Edge which is the best item for as it gives 50% crit and increases crit chance to 240.
Then you should finish mercury treads for tenacity or beserker grieves before static shiv for more damage however to do that you should've started Doran's Shield.
Get a Spirit Visage when ap castors have more ap to burst and no magic pen as Spirit Visage increases life steal and since yasuo has huge amounts it is really good. Randuin's Omen against ad carries who are kiting you really well and burst you as it gives good armor and good passive along with active.Get a warmogs armor when they do initial burst and focus you. Guardian Angel revives you and gives you bonus armor and mr. Frozen Mallet increases kiting potential along with health and attack damage. Furor is for kiting, alactrity is for bonus ms in general, homeguards is for base rush. Last Whisper along with your ultimate means you basically ignore armor. Trinity Force is when they have low armor and you need to burst really fast and you need extra speed,hp, and sheen works really well with your q.