Shiranui sent Zoro out while Liam was battling and the Zoroark conjured an illusion that made him look like his trainer's double while the real Shiranui left for the stairs to the right under the cover of an invisibility illusion.  "[i]I'll save Brandon first,[/i]" he answered, "[i]The fewer people I have with me while I sneak around, the less chance I have of being caught.[/i]"  He was no longer invisible after leaving Zoro's line of sight.