Yasuo's sword's length is about tachi's or even ōdachi's; however, he wears it cutting edge up like the shorter katana.
Yasuo is Japanese masculine given name, rendered as 康夫 "peaceful man" in Japanese localization.
Yasuo is not his birth name, but was given to him when he joined the sword school in an effort to steady his wild nature.
Since his brother is named Yone 米 "rice", Yasuo's birth name might be likewise mundane (e.g. Serizawa Kamo's adult name 鴨 means "duck").
Way of the Wanderer's doubled critical strike chance references Samurai gameplay portrayals in video games, or any high damage-based role meant to deal burst damage to the opposition.
Yasuo and Karma each speak a different Ancient Ionian dialect (possibly two unrelated ancient languages in Ionia, given the lack of sound correspondences & cognates; Yasuo's sounds like broken Japanese and references Kiai)
He references and resembles Miyamoto Musashi and/or Haoumaru from Samurai Shodown via his iconic ponytail design shared with individuals, where in the former's case it is usually a case of a common design for him in fictional media.
Haoumaru himself of course, is also based on Miyamoto Musashi as well. Another note of his is how his Steel Tempest in the Chinese servers is written/dubbed as 斬鋼閃 (Zhǎngāngshǎn, lit. Slashing Steel Flash), which when read in Japanese with the same characters (Zankousen) is exactly the same name as one of Haoumaru's attacks.
Yasuo's taunt in most of his skins (save for Nightbringer) involves him drinking from his bamboo flask, then spitting on his blade to "bless it", a habit that's also shared by Haoumaru in his home series' battle intros.
He references Gray Fox and/Samuel Rodrigues or Raiden, all from the Metal Gear series. The last was further referenced in Yasuo's recall animation pose that is similar to Raiden's when he battled Vamp's robots in Metal Gear Solid 4: Guns of the Patriots, where he holsters his blade by the pommel underneath his foot.
He has one less basic attack animation compared to his other skins, and all three basic attack animations are different from all other skins despite the same animations on all non-recall animations (barring Nightbringer Yasuo).
His voice loses the sound effects and his face can be seen when he jokes, taunts, or dances, where it is shown as normal without any altercations unlike with the other PROJECT skins.
His sword blade turns olive-yellow while Last Breath's bonus armor penetration is active, as opposed to a subtle aura covering his sword.
In this skin, he drinks from a fuel-container which may contain a substance suitable for cyborgs.
The flask he normally drinks from is instead turned into a potion vial in this skin.
Yasuo is an Ionian swordsman accused of treason for allegedly murdering an Elder. He is being hunted down across the island continent the killer employed a wind technique, one that only Yasuo has mastered in the present day.
He crossed paths with Taliyah while on the run, teaching the Shuriman stone mage how to control her powers. When they parted ways, she gifted him a long thread from her handspun wool tunic (the same one he uses to tie his hair up)
Yasuo suspects Riven of being the Elder's killer ("Wait, that technique... huh", "Huh, three swift strikes... ", "Another wind blade?", "Who taught you that?")