Densenken allows user to see the electric and magnetic field lines in their environment. Users train to analyze the reflections of electromagnetic waves they generate creating a sonar-like ability, allowing them to sense invisible attacks, or attacks that come from blind spots.
All living things generate bioelectrical energy, as well as electromagnetic radiation. Densenken practitioners just sense it personally, rather than with the intervention of machines. And it's a known fact that your emotions cause your body temperature/bioelectrical patterns to fluctuate. They can distinguish people by the 'feel' of this aura alone, and don't necessarily need to be able to see them. User’s vision extends very little beyond that of a normal human. They can see into the IR and UV light spectrums, but not all that well. To Densenken practitioners most people are surrounded by a faint, hazy field of energy that changes as their bioelectrical patterns fluctuate.
It also grants them the ability to detect invisible or cloaked creatures and objects by tracking their movements along the magnetic lines. Because of this bioelectrical energy, even an invisible person is going to create a disturbance within users' sensing range.