Reunited Worlds[1] (Korean: 다시 만난 세계; RR: Dasi Mannan Segye) is a South Korean television series starring Yeo Jin-goo, Ahn Jae-hyun, and Lee Yeon-hee.

Sung Hae-sung (Yeo Jin-goo) is a senior high school student.

12 years later, Hae-sung wakes up at the roof of his school building, and he meets Jung-won (Lee Yeon-hee) again.

With the assistance of his friends and Jung-won, Hae-sung sets out to make things right for his family and solve the mysteries surrounding his death and resurrection.

The series is the third collaboration between writer Lee Hee-myung and PD Baek Soo-chan, who worked on A Girl Who Sees Smells (2015) and Beautiful Gong Shim (2016).