Unfortunately, due to the fact I can’t speak Japanese (well, I think it’s Japanese) there is litlle background I can give to help contextualise this footage.
Asia, which is hardly renowned as a hotbed of football violence, witnessed a crazy event in the past few days as a player looking to take a corner was attacked by fan sitting in the stands, who struck his over-sized flag on the footballer’s head as he was preparing to take his kick. The player fell to the floor, but fortunately was able to get up soon after.
Making this event so surreal however was the fact that the police failed to apprehend the supporter in the crowd, and minutes later when a corner was due to be taken from the other side, the fan ran to the opposing corner and attempted to replicate his actions again. This time he was stopped, seemingly by his fellow supporters.
See the footage here.
In secondary footage, eye-witness video captured other fans spilling onto the pitch during the match.
(Any additional information behind this incident is welcome in the commnets.)