Here's some references to clarify Vaer's speculation.
(1) Yuuki's strength is her reflexes, not her sword skills or her experience
Vaermina said:
Yuki's strength was based on OSS
The only time Yuuki used
any Sword Skills in her duel against Asuna was right at the end of the fight. Prior to that, she was able to deflect Asuna's strikes,
including Asuna's
Sword Skills, using only her reaction speed. Asuna also mentions that Yuuki is inexperienced - she never uses any feints, and she falls for Asuna's surprise tactic of using a [<Boxing]> technique.
SAO LN 7 – Ch 3 said:
Asuna's right hand shot forward like an arrow. Those thrusts filled with torque and inertia shot out twice slightly to the left of the center of Absolute Sword's body, and another thrust ingeniously shot out to her right after a short while. It was a regular skill rather than a sword skill, although it wasn't as fast, its aim was more precise. If she dodged to the right to avoid the first two thrusts, she couldn't evade the following one.
Like Asuna thought, Yuuki's body moved slightly to the right to avoid the first two strikes. As her movement stopped, she entered the striking zone of the third hit—
However, as the tip of the rapier was about to hit her chest armor, Yuuki's right hand moved indistinctly. At the same time, sparks appeared to the right side of Asuna's rapier, and the trajectory of the thrust shifted slightly.
…
Tremors filled Asuna's body as she faced this terrifying, lightning fast speed.
…
Asuna was more speechless at her amazing reaction speed. Although she kept hearing about how strong she was, the opponent's unexpectedly cute face put her off guard. She once suspected that the reason Kirito lost was due to negligence or discretion while fighting a girl, but that was completely undeserved. Even he wasn't able to successfully block Asuna's full power thrust even once.
…
Asuna suddenly pulled back her right hand, and at the same time, clenched her left fist and punched Absolute Sword's right side. This was a «Boxing» skill which she learned when she visited the faraway Gnome capital's training field. Even though there was no power because she didn't equip a knuckle-type weapon that it was intended for, it caused a flinch which was impossible without using a skill.
Dong, an impact came from her left fist, Absolute Sword widened her eyes in shock. This was her first and last chance. Asuna didn't hesitate and activated the four-hit sword skill «Quadruple Pain».
Asuna's rapier shone bright red and at the same time her right hand, controlled by the system, shredded the air like lightning.
Asuna was confident that the attack would hit. The opponent's posture was already destroyed and it was also impossible to avoid in terms of distance.
However. Letting the system speed up her right hand, Asuna looked at Absolute Sword's face, and tremors once again filled her body. Even though Absolute Sword's eyes were wide open, there wasn't a hint of panic in her violet eyes. Her eyes were focused on the tip of the rapier.
She could see the thrusts—?
The instant this thought crossed Asuna's mind, Absolute Sword's right hand flashed out.
Like a sword placed on a grinding wheel, a hard, scraping sound continuously rang out four times. Asuna's four-hit combo was accurately parried up, down, left and right, not a single blow hit. Asuna could only see a thin, ink-like afterimage left on Absolute Sword's sword.
Her last hit being parried, Asuna was frozen in a position
(2) The source of Yuuki's strength
The reason for Yuuki's superb reaction time is also explained in the SAO LN's, although you do have to look beyond Mother's Rosario to get the complete picture. It's mentioned in one of the other LN's that the longer a person is linked up with the Nerve Gear, the faster their nerves learn to synchronize with the Full Dive system. In other words, longer time in Full Dive = faster reflexes. (I remember this distinctly because at the time I thought
'this doesn't make any sense from a physiological perspective'. However, it is SAO!canon, and thus Word of God for this story setting).
It's not stated quite as directly in Mother's Rosario, but Asuna's explanations are consistent with Reki's world building, and also excludes the Medicuboid's deeper link from being the reason for her faster reflexes:
SAO LN 7 - Ch6 said:
It's impossible to be so agile unless the player avatar, nerves and the AmuSphere that links them both are all as one.
How much experience did she have to gain just to reach that level?
SAO LN 7 - Ch 9 said:
The Medicuboid was installed with many times the number of pulse generated components compared to the Nerve Gear, and could completely eliminate the feeling of the body, and even had a CPU that had a processing speed that was far superior to the AmuSphere—in other words, was the overwhelming ability Yuuki displayed in Alfheim because of the outstanding specs of this machine?
Asuna had this idea for a moment, but she immediately rejected the notion. Yuuki's amazing sword skills have exceeded the level which a machine's specs could display. In regards to the talent in battle, Yuuki's ability was enough to match Kirito's, and maybe even beat him.
As far as Asuna knew, the reason Kirito became so strong was because he spent much more time fighting on the frontlines than anyone in those two years where they were imprisoned in SAO. If that's the case, how long had Yuuki been in that world created by the Medicuboid—
Before today, Asuna thought that amongst all the users of AmuSphere in the whole world, the ones with the most dive experience should be the old SAO players, including her. But now she knew that she was wrong. This skinny girl lying in front of her was the purest virtual traveler in the world. This was the reason Yuuki became so strong.
(3) Mother's Rosario
Vaermina said:
Actually [Mother Rosario] is never described, so I don't know where your getting that is was just a bunch of thrusts from.
...
I stand corrected, however those weren't thrusts like you claimed they were lunge's and slashes which are more difficult to chain together.
It's also described a second time in Yuuki's duel with Asuna, and the word "thrust" is used to describe the first 10 strikes. The final strike was going to "pierce" Asuna, which indicates an 11th thrust. Slashes don't "pierce".
SAO LN 7 - Ch 3 said:
A counterattack-sword skill!
"Aaah!"
For the first time in the match, Yuuki let out an awe-inspiring cry. Then, she thrust forward with a speed that would've been very hard to avoid even if Asuna wasn't recovering from her skill, and caught Asuna's left shoulder. Slanting directly towards the bottom-right, she executed a five-hit combo without rest. All of them beautifully hit and Asuna's HP bar rapidly decreased and became yellow. She didn't remember a one-handed sword skill like that, which meant it was an «Original Sword Skill». She actually compiled such a fast five-hit combo—
While Asuna was dazed and thinking that, the light of Yuuki's sword didn't fade and she raised it to her upper-left.
It didn't end in five hits. It was still continuing. Finally being released from her skill's recovery time, Asuna pulled herself together and once again trembled.
Supposing Yuuki thrust at her another five times, there was no doubt that her HP would drop to zero. However, it was impossible to avoid.
Rather than uselessly trying to run and getting hit in the back, it'd be better to gamble on a small chance. Asuna put all her energy into her right hand and once again activated a sword skill. The only five-hit OSS which she had successfully compiled, named «Starry Tear».
Red and blue flashes interlocked. Going from Asuna's right shoulder to her bottom-left, the tip of Yuuki's sword intersected with her previous hits and made a cross.
However, Asuna's rapier finally hit Absolute Sword. Drawing the apex of a small star, the five-hit thrust skill pierced the black armor.
They finished exchanging five hits, and there was a moment of silence. Neither of them had fallen.
Absolute Sword's HP bar was reduced by more than half, and turned yellow. Whereas Asuna's HP bar entered the red zone, and there was only a little left. In the first place, Asuna, whose character data was inherited from SAO, had higher HP than ALO players. The astonishing ten-hit combo managed to actually chip almost all of it away, the power of Absolute Sword's OSS was really terrifying, however...
No. Yuuki's longsword was still releasing a violet glow, the sword skill hadn't ended.
Once again pulling back her sword, she aimed directly at the center of Asuna's body, the intersection of the cross-shaped effect.
That is saying, this is the miraculous OSS which Absolute Sword gambled on the duel? Asuna sighed deeply.
Power and speed which exceeded common sense, moreover, beauty which was even greater than those. I have no regrets losing to this kind of sword skill. Stating this in her heart, Asuna waited for the final hit.
The eleventh hit ferociously descended — but suddenly stopped right before it pierced through Asuna. The forcefully interrupted system support released a bright flash and the impact was released into the surrounding air, causing the surrounding grass to radially fall.
(4) Yuuki's duels against Kirito
Vaermina said:
Also she beat Asuna and Kirito in sword duels, which were all about RL sword skill.
I usually refrain from discussing power levels, but it's always annoyed me how people seem to think that Yuuki is a more capable swordsman than Kirito on the basis of her two duels with him. It is clearly stated in the LN that while Kirito did fight her seriously, he
NEVER went all out against her.
SAO LN 7 - Ch 1 - Lisbeth said:
Even if you ask me, for that level of fighting, someone like me can't determine whether they're serious... But Kirito wasn't dual-wielding, so in that aspect he wasn't going all out.
SAO LN 7 - Ch 10 said:
Having defeated Kirito, who made lots of legends—even though he didn't use his Dual Blades skill—«Absolute Sword» Yuuki was crowned the 4th champion of the tournament
And the only time Yuuki does see him going all out?
SAO LN 7 - Ch 6 - Yuuki said:
"No...No way..."
Even the «Absolute Sword» Yuuki could only mutter in disbelief.
He then proceeds to duel wield against 30 high tier players while Yuuki's entire party of 7, including Asuna, takes on a mere 20.
(5) Kirito's decision to zero his stats before he started playing ALO again
Vaermina said:
Depends on a number of factors, Kirito's stats weren't unique among people in ALO given he was able to get back to that level through normal play a couple months after restarting his character.
That is pure speculation. As far as I know, it's not mentioned
anywhere that Kirito was able to regain the stats that he had from Aincrad. If you do find a reference to show that, please show me the quote.
---
(6) Yuuki's sister
On a different matter, while looking up those quotes I discovered that Mother's Rosario also sets out some interesting timeline facts:
- In January 2025 Asuna was freed by Kirito
- Asuna fights the Floor Boss with Yuuki's guild on 8th January 2026. She visits Yuuki several days after that, at which time, Yuuki's doctor says: "Yuuki-kun's parents…died 2 years ago, and her sister died a year ago."
Thus, if TH sticks to the premise that Yuuki's sister wasn't saved by the transition, then her sister would likely have died only a handful of days before the transition.
That should provide plenty of scope for some survival guilt on Yuuki's part, and she should still be grieving for her sister's loss.
Edit:
I forgot that TH has shifted all the dates. In SAO Canon, SAO was launched on November 6th, 2022 and cleared on November 7th, 2024. Asuna was rescued in Jan 2025. In HaLO, the Transition occurs on Jan 21st, 2024, so all the Canon dates should be moved forward by a year to match.