True to its name, the Hotaru Hi-Watt appears as a larger version of the firefly-based HotaruBadnik; it has a circular yellow head with two black eyes and two yellow antenna, a red, cylindrical body with two silver legs on either side, and most notably, a large light bulb which serves as the robot's abdomen.
Stronger and tougher than the regular Hotaru, the Hotaru Hi-Watt possesses levitation and the ability to split itself into smaller Hotarus (which can put themselves back together again), allowing it to disappear at will. Its primary attack is firing a large electrical beam from its light bulb.
In Sonic Mania, the Hotaru Hi-Watt is fought with Sonic, Tails or Knuckles. In Sonic Mania Plus, it is fought with Sonic, Tails, Knuckles, Mighty or Ray.
When the battle starts, the Hotaru Hi-Watt will fly up and out of the arena and deploy a regular Hotaru Badnik which will teleport around the arena four times whilst firing its beam. However, this Hotaru can just be attacked and defeated. After that, two more Hotaru will appear at the top of the screen. These two will be connected by electrical arc which can damage the player if they are caught in it as the two Hotarus fly down.
After the Hotarus' chain attack, the Hotaru Hi-Watt will reappear in the arena on either end of the screen and move across the area whilst firing its beam attack into the ground. The player must take this opportunity to attack the Hotaru Hi-Watt whilst avoiding taking damage from the attack. After it has traveled across the screen, the Hotaru Hi-Watt will fly back up and repeat the pattern. After taking six hits, the Hotaru Hi-Watt will be defeated. The player can then touch the Goal Plate that falls from the sky and finish the Act.