<p>In episode 19, Asuna reports that Leafa thought that Kirito had had an exchange with Zekken during their fight. Kirito then tells Asuna about what happened:</p>
<blockquote>
<p><strong>Kirito:</strong> Um, something was bothering me.</p>
<p><strong>Asuna:</strong> What?</p>
<p><strong>Kirito:</strong> I asked, &quot;You're totally living in this world, aren't you?&quot; Zekken answered with a wordless smile and a charge skill at incredibly speed. That speed was beyond the limits.</p>
<p><strong>Asuna:</strong> &quot;Totally living in this world&quot;? Do you mean they're a really heavy user?</p>
<p><strong>Kirito:</strong> No. I wasn't referring to a single VRMMO. I felt like Zekken was a product of the full-dive environment itself.</p>
<p><strong>Asuna:</strong> What does that mean?</p>
<p><strong>Kirito:</strong> I don't want to give you any preconceived notions. I want you to feel the rest for yourself.</p>
</blockquote>
<p>(Text from Crunchyroll subtitles.) Thus, that she is &quot;totally living in this world&quot; must be the &quot;secret&quot; that Yuuki is referring to; we do not hear of Kirito having any major interactions with Yuuki at any point prior to their duel. Furthermore, Kirito's intuition is correct. Spoilers for the rest of the arc:</p>
<blockquote class="spoiler">
<p> In episode 22, Kirito states his guess that Yuuki is a Medicuboid user and directs Asuna to the only hospital in Japan using the device.
 We then learn that Yuuki is an AIDS patient. She has been using the Medicuboid machine experimentally to alleviate the suffering caused by her health problems. Beyond providing pain relief and alleviating sensory impairments, the Medicuboid can also immerse the user in a virtual reality environment, such as that of the video games being played in the SAO universe.</p>
</blockquote>

CC BY-SA 3.0
2016-06-05T00:16:28.177Z
I don't remember the exact quotes, but this should be the gist of the answer. I can try to put in more details later after taking a look at the relevant episodes.
Maroon
CC BY-SA 3.0
2016-06-05T00:19:59.697Z
That's what I thought too, but through out the episode or even the entire arc, we don't know what Kirito had exactly said. Can you affirm this with some evidence ?
Haider
CC BY-SA 3.0
2016-06-05T00:24:35.547Z
I seem to remember Kirito's key insight here being that not only had Yuuki been full-diving for a long time, but that she had to have been full-diving longer than him, which meant that she couldn't have been an SAO survivor. And then from there, he worked out what her actual situation was.
senshin
CC BY-SA 3.0
2016-06-05T01:03:37.740Z
@senshin: thanks. I don't recall anything more specific than an observation from Kirito (reported by Lisbeth) that Zekken wasn't an SAO survivor, and moreover, that his dual-wield skill ought to have gone to her had she been in the game. But I also only know the anime, and it's not a franchise that I've followed too seriously.
Maroon
CC BY-SA 3.0
2016-06-05T01:04:21.323Z
@Haider: found the relevant dialogue.
Maroon
CC BY-SA 3.0
2016-06-05T08:18:24.913Z
Well, the dialogue does give an idea about what Kirito would have said relating to her secret.
Haider
CC BY-SA 3.0
2016-06-05T00:15:30.330Z
2016-06-05T01:01:42.463Z
2020-06-17T09:17:53.303Z
Maroon
<p>What did Kirito whisper during his fight with Zekken before which he was  defeated? In episode 20, Asuna asked Zekken (Yuuki) about this and she replied that Kirito had "figured out [her] secret".</p>

<p>What was the secret?</p>

CC BY-SA 3.0
2016-06-05T01:16:05.303Z
Note that the question is about why, despite thinking he's strong, Yuuki didn't "hire" Kirito, rather than what their exchange in the duel was about.
Maroon
<sword-art-online>
How did Kirito find out Zekken's secret?
# How did Kirito find out Zekken's secret?
Posted by: username_0 on 2016-06-05
What did Kirito whisper during his fight with Zekken before which he was defeated? In episode 20, Asuna asked Zekken (Yuuki) about this and she replied that Kirito had "figured out [her] secret".

What was the secret?
**Tags:** sword-art-online
> **Comments:**
> **username_1**: Note that the question is about why, despite thinking he's strong, Yuuki didn't "hire" Kirito, rather than what their exchange in the duel was about.  
---
## 1 answers
### Answer by username_1 on 2016-06-05. Score: 6 | Accepted answer
In episode 19, Asuna reports that Leafa thought that Kirito had had an exchange with Zekken during their fight. Kirito then tells Asuna about what happened:

> **Kirito:** Um, something was bothering me.
>
> **Asuna:** What?
>
> **Kirito:** I asked, "You're totally living in this world, aren't you?" Zekken answered with a wordless smile and a charge skill at incredibly speed. That speed was beyond the limits.
>
> **Asuna:** "Totally living in this world"? Do you mean they're a really heavy user?
>
> **Kirito:** No. I wasn't referring to a single VRMMO. I felt like Zekken was a product of the full-dive environment itself.
>
> **Asuna:** What does that mean?
>
> **Kirito:** I don't want to give you any preconceived notions. I want you to feel the rest for yourself.

(Text from Crunchyroll subtitles.) Thus, that she is "totally living in this world" must be the "secret" that Yuuki is referring to; we do not hear of Kirito having any major interactions with Yuuki at any point prior to their duel. Furthermore, Kirito's intuition is correct. Spoilers for the rest of the arc:

> In episode 22, Kirito states his guess that Yuuki is a Medicuboid user and directs Asuna to the only hospital in Japan using the device.
> We then learn that Yuuki is an AIDS patient. She has been using the Medicuboid machine experimentally to alleviate the suffering caused by her health problems. Beyond providing pain relief and alleviating sensory impairments, the Medicuboid can also immerse the user in a virtual reality environment, such as that of the video games being played in the SAO universe.
> **Comments:**
> **username_1** (2016-06-05): I don't remember the exact quotes, but this should be the gist of the answer. I can try to put in more details later after taking a look at the relevant episodes.  
> **username_0** (2016-06-05): That's what I thought too, but through out the episode or even the entire arc, we don't know what Kirito had exactly said. Can you affirm this with some evidence ?  
> **username_2** (2016-06-05): I seem to remember Kirito's key insight here being that not only had Yuuki been full-diving for a long time, but that she had to have been full-diving longer than him, which meant that she couldn't have been an SAO survivor. And then from there, he worked out what her actual situation was.  
> **username_1** (2016-06-05): @senshin: thanks. I don't recall anything more specific than an observation from Kirito (reported by Lisbeth) that Zekken wasn't an SAO survivor, and moreover, that his dual-wield skill ought to have gone to her had she been in the game. But I also only know the anime, and it's not a franchise that I've followed too seriously.  
> **username_1** (2016-06-05): @Haider: found the relevant dialogue.  
> **username_0** (2016-06-05): Well, the dialogue does give an idea about what Kirito would have said relating to her secret.  
---
