Amazon.com : Topeak Hexus II Multi-tool : Bike Multifunction Tools : Sports & Outdoors

The chain tool requires you to insert a hex wrench in the top, to twist it. You can't do it by hand. Does that mean you need to carry a separate hex wrench to use the chain tool?

I have that tool and no. The black sides come off and are the tire levers, one of which also has the hex key built into it for the chain tool.

According to two reviewers it is "flexible" and bends easily and the tire tools 'broke'. That suggests an emergency use only and a tool that can't be
expected to apply much torque. How useful a tire tool is depends on how easy your tire/rim combo is to R&R. Some basically don't need tools to
replace the tire and only a bit of pry to get the first bit of tire over the rim, others require 20-30 minutes of effort to do the same (eg my bent!!).
On the one occasion when an 8mm allen head crank bolt loosened up on a ride, an all in one tool was unable to apply enough torque to get me
more than a few miles.

My preferred tool kit is two of the ParkTL 1.2 tire tools, an MT1 wrench and the CT5 chain tool. It is reasonably light and versatile. I have only
needed the chain tool on three occasions over the past 10 yrs, but it is indispensable when needed. I also carry a few speed links for the chain
some tire patches and a never opened tube of glue, but since I also always have two spare tubes I have never used the patches. A few rectangles
of tyvek type polypro nonwoven paper 1" sq and 1x2" complete my rescue kit for the rare side wall rip in a tire. These are so tough they can
easily hold 60-80# pressure in a tube for rips in the sidewall-enough to get you home.

Buy this tool instead:

https://www.amazon.com/Crank-Brothers...ers+multi+tool

The chain tool is one piece, and I can attest to its working well enough that a twelve-year-old can operate it.

Two-piece chain tools strike me as being too fiddly. Not sure why they are even made.

It came with the Hex. I've used it a few times without any problem.

My chain tool of choice is the Nashbar Woodie. A little heavy, but cheap, and pretty comprehensive: chain, tire lever, allens, torxs, screwdrivers, spokes, etc, and even a 'metatool' for tightening or loosening how tight the tools rotate out -- or perhaps disassembling the whole shebang?