Please give a valid explanation instead of saying theyre just opposites

The first word "though" (or although) represents a shift in sentence so the two blanks have opposite meaning from each other. The "by contrast" is just adding to the fact that two blanks are opposites.

We can simplify the sentence something like this

Although Darek was fascinated by the (i) _____ behaviour but he himself has (ii) _____ comportment (or behaviour).

So the most suitable answers choices are unorthodox (contrary to what is usual, traditional, or accepted) and conformity (behaviour in accordance with socially accepted conventions).