According to How to use II:


  The owner of the note can recognize the image and voice of the original owner, i.e. a god of death.


Therefore the only explanation for Light being able to see Ryuk would be, that Ryuk is the original owner. But how did Ryuk become the owner of Sidoh's Death Note? As I explained at How did Ryuk trick the King of Death Gods?, it is because of How to Use XII:


  If you lose the Death Note or have it stolen, you will lose its ownership unless you retrieve it within 490 days.


Ryuk became owner of Sidoh's Death Note because of this rule. It wasn't until chapter 65 that Sidoh realized that he had lost his Death Note, which is 6 years after Ryuk first dropped the Death Note down to earth. If it took him at least 6 years to realize he had lost his Death Note, it would be safe to assume that Ryuk had already found the Death Note 490 days before he dropped it down to earth, claiming ownership and becoming tied to that particular Death Note.

Why was Ryuk tied to Light's Death Note?
Update/Re-write

There has been a lot of ambiguity over what i'm am trying to do with this question so I have decided to give it a full rewrite. I'm really sorry for the confusion. If you want to see the background please see the edit history. I hope things are clearer now..

I have some data made up into the following fashion:

datac =
  {
   data1 = RandomReal[1, {7, 3}],
   data2 = RandomReal[1, {13, 3}],
   data3 = RandomReal[1, {19, 3}],
   data4 = RandomReal[1, {16, 3}],
   data5 = RandomReal[1, {5, 3}]
   };


data1 through data5 are subsets of a multivariate dataset with 3 independent variables. data1, for example, is composed of 7 individual data points (each with 3 variables).

If I use the following function: 

Needs["StatisticalPlots`"]
pairwisecol[data_, col_] := 
PairwiseScatterPlot[data, 
                      PlotStyle -&gt; col, 
                      DataTicks -&gt; True,  
                      DataLabels -&gt; {"x", "y", "z"}]


I can create a combined plot comparing the various subsets. E.g.

Show[{pairwisecol[data1, Red], 
      pairwisecol[data2, Blue], 
      pairwisecol[data3, Green],  
      pairwisecol[data4, Purple], 
      pairwisecol[data5, Orange]}]




This curently has the major drawbacks that each subset has to be defined and have a colour explicitly assigned to it. Also, Show in this instance overlays all of the DataTicks etc, rather than just the elements from the first plot (as is normally the case with Show[{Plot1,Plot2}]).

What I'm looking for is a way to use the whole (partitioned) dataset datac to generate such a plot/diagram. i.e. something like,

Show[pairwisecol[#, Red] &amp; /@ datac]


but, with Red being replaced by a series of colours to represent each subset (like in the plot shown).

...Alternatively, starting with a 2-level list e.g.

datap = RandomReal[1, {60, 3}];


and a definition of sublist partitions,

parts = {7, 13, 19, 16, 5};


or

partspos = {[[1;;7]], [[8;;20]], [[21;;39]], [[40;;55]], [[56;;60]]};


then defining a function something like:

pairwiseP[data_, partlist_] := ...


that would partition datap into appropriate sublists, create a series of PairwiseScatterPlot's (each with a different plot colour) and then combine them using Show. 

Note that this example has n = 3 independent variables. I am looking for a method that works for 1 &lt; n &lt; ~20.

Can anyone suggest how to do this?
