Certain notes can be written in two different ways, although they sound the same when played. Such notes are referred to as enharmonic notes. E.g. the note D# has the same position on the keyboard as the note Eb, so D# and Eb are said to be enharmonic notes. There are further examples of enharmonic notes in the following lessons.
The leading note of the E harmonic minor scale is D#. The leading note of a harmonic minor scale is never indicated in the key signature.
The key signature for Em contains one sharp (F#). This is the same key signature as G major. Em is the relative minor key of G major. Because the above song ends in an Em chord, it is in the key of E minor. Another way of determining if a song is in a major key or its relative minor is to look for the leading note in the melody (i.e., the sharpened 7th note contained in the harmonic minor scale). The song Minka contains the leading note of the E harmonic minor scale (D#) which is another indication that this song is in the key of Em.