Benkei is a travelling monk who's dream in life is to collect 1000 swords. He tells Amaterasu and Issun when he is first met in Sei' an City that he already has 999 swords but it is unknown whether these are just regular swords or if they are special and sacred. He carries a pike in his hand but he also appears to have quite a lot of swords stored in his satchel.
Benkei is first met in Sei'an's Commoners Quarters where he is in charge of operating the bridge to get to Aristocratic Quarter. He has his heart set on catching the legendary "living sword" and will not raise the bridge until you help him catch it. This involves buying the Blinding Snow rod from the Sei'an items Merchant and giving it to Benkei for you to help him fish which will start a fishing Mini Game.
To Benkei's amazement the "living sword" is not actually a sword but a giant cutlass fish, however he stays true to his word and raises the bridge. He thanks Amaterasu and Issun for introducing him to his new obsession, fishing, as he now feels sword collecting was a waste of time.
He can be then found near the Mermaid Spring in Sei'an's Aristocratic Quarter and he will fish with Amaterasu whenever she wants to.
Benkei makes a reappearance in Okamiden, although, he has a slight costume change. He was a Sailor on the Goryeo before it was sank by the Water Dragon. He learns about the "Living Sword" during his time spent aboard. When Kurow and Chibiterasu first travel back to the Goryeo, Benkei challenges them to a duel for ownership of Kurow's sword as he mistakenly believes Kurow is concealing one in his flute. However, he allows them to continue on their way when the Old Sailor tells him that he should make the Living Sword his 1,000th sword. Although sceptical, he eventually falls for the Old Sailor's trick as he does not know the Living Sword is actually a cutlass fish. They when he survives the sinking of the Goryeo, he travels to Sei'an to find the mysterious "living sword" and this is where Issun and Amaterasu meet him in Okami].
 Based On
Benkei is based on the character called Saitō Musashibō Benkei in the story "Yoshitsune and Benkei". This is also the story Waka's character is based on. This Benkei was a great warrior monk who fought men and took their swords upon their defeat. When he had collected 999 swords he fought Yoshitsune in the hope of obtaining his one thousandth sword, however he was defeated. He then became Yoshitsune's right hand man until his death.
We see that references to this legend carry on in Okamiden as he challenges Kurow to a duel for what he believes to be a sword in his flute. Kurow is a living doll that was created by Waka and modelled after him. The character that Waka is based on in "Yoshitsune and Benkei" is the person that Saitō Musashibō Benkei challenges for his 1,000th sword in the legend.