WMG / Tokyo Jungle

Tokyo Jungle is a part of an ARG of some kind that is yet to be solved.

Near the top left area of Shibuya Station, there's a road blocked off by a large piece of building rubble. Despite the fact that all humans are gone, when you stand next to it during a run, you can faintly hear a sad tune being played on some kind of wind instrument, independently of the current bgm. No explanation exists in-game or in real life for this bizzare sound.