第三幕　土蜘蛛

With their new companion Sadamitsu, Raiko and Tsuna approach the caves where the Tsuchigumos dwell. Inside the caves they meet with Kuzume, a young girl from the village kept in captivity by the Tsuchigumo clan. Raiko and her team advance deeper and deeper inside the cave, and in the innermost recess of this underground world, they finally see an altar emanating a holy light: it's the Magatama! But a huge shadow steps before them: for Raiko and her friends, it is time to face Hoshikuma, the feared commander of the Tsuchigumo clan!

貞光を仲間に加え，土蜘蛛の住む洞窟に向かった光と綱。 洞窟の奥へと進む光の前に，大勢の土蜘蛛族の姿が映る。三人の手勢で討つには多すぎる敵。自ら囮役をかってでた綱は, 土蜘蛛族の中に身を投じる。 光たちは，はたして土蜘蛛の頭領、星熊を討ち倒し、勾玉を奪還することができるのか。