Junnosuke Kuroda is a ninja master and faithful servant to Tatsunoshin Suou during the Period of the Warring States. After the failed assassination attempt on Kiyotada Sumaru which claimed the life of Tatsunoshin's lover Maihime Amano, Junnosuke reluctantly fulfills his master's final wish to burn down Sumaru Castle with the lovers and the incapacitated Kiyotada still inside, and escapes with his life.
He later took on the name Fuyou, and founded the martial arts school of Mokujinken, or the Fist of the Wooden Man. Upon his death due to natural causes, his spirit remains in limbo, awaiting the day when his master would call upon him to once more exact revenge on Kiyotada Sumaru.
If Maya fills up the offertory box at Mt. Mifune (this can only be done while en route to the Morimoto Sanitarium), Junnosuke Kuroda's spirit will appear upon the calls of his master Tatsunoshin in Sumaru Castle, and can be summoned as a Persona of the Fool Arcanum. Along with Maihime Amano's Dance of Protection and Tatsunoshin Suou's Mighty Swing, his Deadly Needle move can be used to cast the Fusion SpellTenchu-Satsu, which will instantly destroy Kiyotada Sumaru's monstrous Gozen form in a single blow.
On a darker note, it is implied the legend of Amano, Suou, Kuroda and Sumaru is a fake spread by Nyarlathotep, to induce the party to alter history with rumors of a past that never happened.