S02E35: The Seven Vongola Rings

Dino manages to fend off the swordsman, Squalo, and explains the situation: a subgroup of the Vongola Family called The Varia is after the Vongola Rings which are held by the leading members of the family, which he then proceeds to give to Tsuna and six other people. They have ten days to train in order to become strong enough to fight off The Varia. Meanwhile, Tsuna's father returns.