B3-NK1 wears a yellow armor with purple shoulder-neck and waist pads, a number of blue beads and black gloves with gold linings. He has green facial features. He also carries a naginata.
In the anime, he is eager and hard-working in his quest for the "Hero's Screw", which he believes he could awake the true power of his naginata.
Using his naginata, B3-NK1 can pierce through modern technology devices without making holes in them, and uses it for looking for screws needed for said devices to work in order to assimilate them with his weapon and forging the "ultimate weapon". In particular, he looks for Heroic Screws (Japanese: 英雄のネジ,Eiyū no Neji), special screws that represent the souls and powers any form of machinery, and it's said that collecting 1,000 of them will awaken the true power of his naginata.
Befriending (YW2): "You guys are pretty interesting. Fine! I'll go with you."
Loafing: "Lemme just rest..."
Being traded:"Re-calibrating friendship-recognition software... Friendship initiated. *beep*"
Receiving food (favorite): "Yep, that's tasty!"
Receiving food (normal):"It's all right..."
Receiving food (disliked):"Can't stand it!"
Freed from Crank-a-kai: "I'm finally out of there! Thanks!"
B3-NK1 appears in EP023, in which he causes some of the electronic artifacts in the Adams House to suddenly stop working. When confronted by Nate, he reveals he caused these malfunctions in his search for the "Hero's Screw", which he states that they can awaken the true power of his naginata, collecting his 998th from Nate's air conditioner, and the 999th from the vacuum cleaner near Jibanyan, Nate, and Whisper. To fix B3-NK1's messes, Nate summons Robonyan, who is then attacked by B3-NK1's polearm when the Yo-kai notes Robonyan's metallic body. However, Robonyan oddly turns out to enjoy its piercing, to the point where he kept prodding B3-NK1 to keep searching him for a Hero's Screw despite his denials to the group when confronted on it. Suddenly, Robonyan begins extending his limbs, tails, and neck, then quickly retracts them, and falls off of B3-NK1, leaving behind a Hero's Screw, and one of the best in the collection to boot, and assimilates it with his polearm, causing it to assume a brand new form. B3-NK1, out of gratitude, gives Nate his Yo-kai Medal.
In EP027, B3-NK1 was seen in Yo-kai-lifornia where he is among the Yo-kai waiting in line for the Yo-kai Watch Model Zero to go on sale.