Kansuke returns home in Mikawa Domain after 15 years. He brings the decapitated head of the samurai of the Takeda army he killed to save Mitsu—he have planned to show it as a display of his prowess in order to be taken into the service of the Imagawa clan. Coming back, Kansuke finds that his adoptive father now has a natural son. The father who wants the son, not Kansuke, to succeed him steals the head and tenders it to one of the warlords under the Imagawa clan as the son’s achievement. Kansuke decides to rename himself Yamamoto Kansuke, the family name of his real parents, and leaves Mikawa for Suruga, where his was born. In Suruga, Kansuke happens to know his elder brother Sadahisa is involved in a conspiracy against the head of the Imagawa family. For knowing the secret, Kansuke is attacked by a group of assassins directed by Sadahisa. Kansuke has to leave home again.
武田家の武将の首を持って１５年ぶりに勘助は三河国牛窪に帰ってきた。首を手土産に今川家への仕官を果たし、幼い頃に養子に入った大林家の家督を継ぐ決意だった。勘助はそもそも駿河国の地侍・山本家の次男として生まれたが１２歳の時、実の父母が出家を勧めたのに逆らい、同情した大林勘左衛門（笹野高史）に拾われ、以来大林家の嫡男として育っていた。だが、戻ってみると養父母の間には実の子が生まれており勘助は厄介者扱いだった。しかも勘助が討ち取った首を隙を見て奪い、実の子の殊勲として届ける有様。勘助は大林家を捨て以後は山本勘助と名乗ると宣言し故郷・駿河に向かう。しかし、そこで信じられない敵が立ちはだかる…。
