The Trial of Pohjola Episode 16

After learning from Ursula and the Shiny Rod that she needs to find something she is lacking in order to unlock the fourth word, Akko joins Lotte and Sucy as they visit Lotte's home in a remote Finnish village. The next morning, however, they discover that Lotte's parents and their neighbor have become infected with the rare Greenman Disease, which will gradually turn them into moss until they wither away...