Nagasarete Airantō : ながされて藍蘭島 - "Hyakkokute, Kōritori" (ひゃっこくて、氷とり) Episode 11

Ikuto wakes up to find that Suzu has a fever. He is told by her grandmother to get ice, but finds out that all the island's stored ice has been eaten by Kuma-Kuma, Kamo-Kamo, and Kagami (Yukino's mother). Thus, he has to go to the island's mountain Mt. Fuji to get some. After going all the way up the mountain and back again in one day, he finds that Suzu is completely recovered, but he himself has a fever from the changes in temperature and fatigue.