Does Dual Wield drain HP? When Kirito fights The Gleam Eyes this is the first time he uses his Dual Wield ability which was the reason why he had a second sword commissioned by Liz, after he killed the boss his HP was quite low.

Before he uses it he's hesitant in using it, was this because Dual Wielding drains HP when active or was his hesitation more to do with the ability becoming more widely known?
It was clear that Kirito was keeping his dual-wield ability a complete secret. Nobody knew about it - not even Asuna. This was evidenced by the fact that Asuna questioned Kirito about why he isn't using Liz's sword and suggested that he was "hiding something" from her.

So Kirito hesitated because be knew that using his dual wield in front of everyone would blow that secret wide open. But he had no choice. It was do or die.



Getting back to the question, there is no evidence in the anime to suggest that dual wielding drains HP. But you could infer other drawbacks such as tying up both hands thus preventing the use of a shield.