Usobuki

Usobuki (うそぶき, lit. False Bud) are the mushi that create the Harumagai (false spring). They feed on the life force of small creatures, and often take form of butterflies in winter and flowers in spring. The Usobuki's metamorphosis from its butterfly form to its flower-like form, signalling the end of Harumagai and thus causing the victims to wake up.