Anyone who is mildly interested in the Harry Potter series and has not been living under a rock for the last couple of decades would know who Voldemort is. The character is famous as one of the most notorious villains and has made quite a following for him. Ever since the Harry Potter series ended, reports mentioned that Voldemort has been roaming around many cities of the world and has moved to our world.
This notion was amplified by these girls, when they sat for a quick picture in the park. What looked like a really quite and calm picture was aggravated by the presence of Lord Voldemort in it and the people on their social media couldn't stop noticing him the dark wizard sitting in the background. Maybe Voldemort wants a dual with these two here.