hatsune miku, megurine luka, gumi, ia, and kisaragi shintarou (vocaloid and 9 more) drawn by inazumrai

Redska said:
Why is Luka tagged here? Is she supposed to be the second one from the left? They share the arm things, similar dress and boots so I she qualifies...

Yes; the characters in the background are cosplaying from various Vocaloid songs, and that one I'm fairly sure is representing Luka Luka Night Fever. (The bit in the video where two travelers stay behind is generally interpreted as a nod to samfree and PowapowaP.)