Beam

From the neck down Beam looks like a brawny young man, dressed in nothing but a pair of swim trunks. The upper half of his head, though, is all shark: a pointed snout and fin sit where a face would be, leaving him with no apparent eyes, a mouth of razor teeth, and a crop of short, bristling black hair beneath. When he taps into his devil heritage he can swell that head into a giant shark's skull studded with three sets of eyes, or go further still and remake his whole body into a shark propped up on several long fins that act as legs.

Beam comes across as odd, childlike, and guileless. Toward almost everyone but Denji he is hostile and withdrawn, with little interest in socializing. Denji is the exception because Beam reveres the Chainsaw Devil, falling in behind whatever harebrained scheme the boy cooks up and shielding him at every turn. That devotion runs so deep that he will pour his own blood into Denji to bring him back, heedless of the damage it does to himself. He relishes a good fight, throwing himself joyfully into swarms of zombies to eat them, though Reze frightened him badly enough to send him running, even as he swung back at her once escape was off the table.

Beam debuts among the Special Division 4 hunters who raid Akane Sawatari's hideout, bursting up through the ground, swelling his head into a shark's maw, and shredding a pack of zombies before being knocked back by the Violence Fiend.

When Power is pulled off duty for overfeeding on blood, Beam asks to take her place as Denji's partner and is delighted to get it, trailing his new idol by gliding through the floor and crowing 'Lord Chainsaw' at every chance. He earns his keep when Reze ambushes Denji on a date; Beam scoops him up, recognizes by scent that she is the Bomb Devil Hybrid, and flees, taking her explosions head-on until he is overwhelmed. He carries the wounded Denji to a Division 2 training center, warns Aki that the Bomb Devil serves the Gun Devil, and stays at his side through the running battle. After Reze fells Denji, Beam joins the Angel Devil in reviving him with blood and explains how the Chainsaw Devil once used his chains to move. Denji then has Beam shift into his full shark shape and rides him like a mount, the two of them tearing through the Typhoon Devil's vortex to kill it and wounding Reze. When Reze strikes from overhead, Beam tucks Denji inside his mouth to spare him and takes the hit himself.

Later, Makima sends Beam to back Denji during the assassin crisis. He saves him from Long inside a department store, but the fight goes wrong: the Curse Devil seizes a bleeding Denji, Tolka kicks Beam senseless, and everyone present is dragged down to Hell. There the Darkness Devil severs Beam's arms along with everyone else's. Undeterred, Beam pushes blood from his severed arms into Denji's mouth and tugs his cord to wake him, pleading for their wish to be granted, only for the Darkness Devil to slice him apart and end his life.