Sword
Tie a squid to a knife and you get a sword! Knives are too small to be considered a sword on their own. That's why you strapped a squid to it. They're the right shape, kinda pointed, so no one will know it's just a knife.
けん
つるぎ
None
You learned how to make swords this way from Ken (けん) the samurai. He put his own little squid buddy on his knife and now no one realizes it's not a sword!