Seon Jae-chan, the 27-year-old young guide team leader, was a model of a success-oriented human being and was on the path to promotion by going straight ahead regardless of the means.
He was deployed in an operation to eradicate the anti-government group 'Black Swan', but was attacked.

At the end of his life, he closes his eyes with tears of regret. And when he opened his eyes, it was 6 years ago.

Jae-chan, now 21 years old, once again makes thorough plans for his future.
Unlike in the past, when he was only obsessed with his own success, this time he has the goal of ‘contributing to precious people’.

He lists major events surrounding the people around him, including his crush, Esper Go Woo-jin, and reflects on his goal.

However, unlike his previous life, Go Woo-jin does not avoid Jae-chan, but rather gets closer to him... ?!