Robotperson

The word 'Cosplay' describes what was going on, a contraction of 'costume' and 'play'.

It's not simply people dressing up in a niche fashion, which is what you'd assume if it were happening in the UK. There's an element of fantasy, of dressing up like your favourite anime heroes or heroines. You could read it as another example of Japanese adult childishness, a quality which is broadly accepted over there and stigmatised over here.