If you put the and symbol in between your tag searches in the search field it should yield better results. You can also use the "+" symbol.
Example:
Nakadashi & condom
However it is important to note that this search field also applies to the words used in the description field. Beyond that it also still leaves. A few chapters out when you search like this.
When you click the link above the first thing you see is the
Daddy Substitute Illustration , it is tagged with Nakadashi and it has the word condom in the description.
I forget the exact reason, but it was stated that the tag descriptions were removed from the site to avoid trouble of some sort, or something like that. However please don't quote me on that.