The Last December is about an 18 year old girl with lung problems. She has stayed in the hospital for a large part of her life and one day, she finds out that she only has a month left to live. Tired of the treatments and medicines that didn't help save her, she go on a trip outside the hospital to fulfil her bucket list with the help of a boy who broke his arm in a recent car crash.

Along the way, they make friends with a mysterious new guy, who is unwilling to reveal much about himself to the other two. Together, they will help the girl fulfil her dying wishes, which includes some things like riding a motorbike, watching the sunrise, having her first kiss and visiting the amazing town of Cornucopia.