To be held in high regard as a native-level Japanese speaker whilst simultaneously keeping a haughty attitude isn’t quite as difficult as it may seem thanks to the gamesman’s version of the old playground favourite “well, if you don’t know I’m not going to tell you!”
To fully understand the Japanese is a bonus but not required; you simply pretend to listen and at choice moments in the conversation attempt to join in with a witty or poignant remark. You mutter a “well…” or “um…" and wait until the people in conversation turn to you with expectant glances eagerly awaiting your input. You then brush it off with a dismissive “nah…” or “um, no, nothing, forget about it” as if to say you thought better of it and decided to not bother anyway.
The result is that the people around you perceive you to be either very humble, as if you decided your remark was unworthy, or haughty, as if they were unworthy to receive the remark; either is a good reaction for the gamesman. Most importantly, though, they will conclude that you have been able to follow the conversation closely so therefore your Japanese must be of a very high level.
As you can imagine no actual Japanese skill is required, just a keen sense of timing, but people will go round telling others what a master of the language you are.
A slight variation of this is the subdued chuckle: simply observe the crowd talking and whenever more than a few of them burst out laughing it is a safe bet to assume something humorous has been said. At this point, even this late in the proceedings, you should let slip a subtle “heh” to show you did understand the joke, even if you didn’t, and that, though slightly amusing, it wasn’t quite funny enough for you to guffaw at. The effect on the targets is similar to the technique above; they will think your Japanese is good enough to get the joke, but they will need to try harder if they wish someone in your high position to appreciate it fully. You are after all a serious and sophisticated foreigner and not laughing out loud at the jokes shows them what a base sense of humour they have.
The advanced gamesman may litter these tactics with a sprinkling of “so desu ne!” (“Isn’t it just!”) or “so ka?” (“You don’t say!”) remarks but be aware that the chances of being found out increase, especially if you have no inkling as to the general slant of the conversation.
Before long your perceived skill in the Japanese language will be legendary.