Ikkakumon's Harpoon Torpedo

As Joe begins to feel responsible for the group's safety, he decides he must explore the surrounding area by himself, and ends up in trouble when a nearby Unimon is struck by a black gear.

Synopsis
The kids find themselves walking through some cold weather, and consider finding a cave they can sleep in. To their relief, there are some hot springs straight ahead, and strangely enough, a fridge full of eggs. After eating, Tai suggests climbing the nearby Infinite Mountain to get a better view of the area, but Matt argues that it would be much too dangerous. Joe prevents a fight breaking out between the two, but the matter remains undecided. So, while everyone is asleep, Joe goes off towards the mountain on his own, followed quickly by Gomamon. Whilst up there, the pair see the Digimon Unimon, who is struck by a black gear. At that moment, Tai and Sora arrive on the scene to help. Joe attempts to remove the gear himself, and Gomamon ends up rescuing him by becoming Ikkakumon, who uses his Harpoon Torpedo to destroy the gear once and for all. After the fight, they manage to reach the top of Infinite Mountain, where they finally realise their location - an island, with nothing but water for miles.

Digivolutions
(Number indicates order of occurrence.)