ペンライト

ペンライト – penraito. penlight, light stick, or blade for the Kingblade varieties. These are LED-powered instruments that generate light. They are normally used during concerts as a way to communicate your presence and participation to the artist. They generally run on AAA batteries and come in many sizes and shapes (though it is increasingly becoming standardized), colors, designs, and intensities.

One thing worth noting is that these are classified as support goods (応援グッズ; ouen-guzzu) along with towels and Japanese fans or uchiwa (団扇) with their customized decorations.