how old is nezuko

Nezuko Kamado from Demon Slayer is biologically 12 years old at the start of the story and chronologically 14 years old considering the two years that pass during the series. Mentally, due to her demon transformation and prolonged deep sleep for regaining power, she often appears and behaves closer to 12 years old. By the latest seasons, she is close to 15 biologically but still mentally about 12-13 years old. Nezuko also has the ability to change her physical appearance and size, which complicates perceiving her age visually.