When Sun Ho meets a girl named Oh Kang Hee and falls in love with her, his purposeless life turns upside down. He even takes a further step and applies to the school Kang Hee is applying to. All Sun Ho cares about is getting accepted so that he can be with her. However, when he thought he almost made it, someone he’d never expect to see shows up and gets in the way.

Sun Ho can’t believe the fact that his interviewer is Dong Man from the illegal wire transfer happening. However, Sun Ho eventually gets the acceptance letter. Meanwhile, to become an officially registered student at the Police University, one must endure the exhausting Chungram Training and its training professors.

In order for Sun Ho to stay at the Police University, he needs to carry his unit to a victory at the last round of the training. He even asks Dong Man for a piece of advice, but to no avail. Meanwhile, Dong Man realizes that there is something fishy going on at the university regarding the illegal gambling site.

After hearing that Chul Jin, his partner, has been ambushed, Dong Man closes in on those who are responsible for the illegal gambling site. However, without hard evidence to prove anything, Dong Man faces a dead end. Meanwhile, Sun Ho finds out who Dong Man really is when Dong Man asks him for help, and Sun Ho contemplates whether to accept his request.

Dong Man accepts that even he may be carried away by emotion at times while investigating cases, and he decides to let Sun Ho in as his partner. The duo starts to dig deeper into the case in which Hyuk Phil is the prime suspect. Meanwhile, Sun Ho’s behavior keeps getting on Kang Hee’s nerves.

Sun Ho does not remember anything that happened on the night he passed out, and Kang Hee can’t believe that he cannot even remember their first kiss. Meanwhile, Sun Ho must win the prize at the Chungram Sports Festival in order to make up for his mistake. However, at the crucial moment, he gets a signal that indicates the presence of a prime suspect.

Dong Man is certain that he would finally catch the culprit this time with Sun Ho as his partner, but it is none other than Chul Jin who shows up as a new professor. As the investigation hits a dead end, Dong Man begins to take extreme measures in pursuing the search, but Sun Ho does not agree with his way of handling the situation and stands in the way.

Dong Man is having difficulties accepting the fact that every piece of evidence points to Chul Jin’s being the culprit, and that’s when the questions for the upcoming exam get leaked. Sun Ho and the gang put everything else aside to prove that Dong Man has been framed. However, for some reason, Dong Man decides to confess that it was his doing.

When Chul Jin confesses that he was in charge of the exam leak case, it puts Dong Man in an awkward position. Although Dong Man’s intentions were pure, he realizes that he’s doing more harm than good to those around him and decides that it’s time to make changes. Meanwhile, Sun Ho and Kang Hee also find their own reasons to join Dong Man’s investigation.

Dong Man has left the Police University without knowing that a burner phone that Sun Ho has been tracking just retrieved a signal. Sun Ho then assembles a unit with Kang Hee and a few others to investigate the location pinpointed by GPS. Meanwhile, Dong Man focuses on what he can do by himself to solve the case as he comes across important information from Kang Hee’s mother.

The culprit behind the illegal gambling site has been caught, and the students continue to enjoy their summer vacation. However, Dong Man can’t get the case out of his head and continues to look for missing pieces. As the new semester begins, Sun Ho, Kang Hee, and others focus on their study, and that’s when Sun Ho receives a message from a stranger.

It’s likely that the enemy is within the organization, and Dong Man now has to suspect his colleagues and friends. At the same time, a stranger sends Sun Ho the statement he wrote when he was caught stealing illegal gambling funds. Sun Ho can’t request help, nor can he tell Dong Man about the stranger. Sun Ho hits a dead end.

Sun Ho just can’t stay still and do nothing while the bad guys get away with what they want, and he decides to put his decisions into action. While doing so, Sun Ho has to decide whether he’s going to save himself or Dong Man. Meanwhile, those who tried to help Sun Ho and Dong Man also get themselves into trouble.

The ledger with recordings of illegal transactions is found by Sun Ho, but after going over the ledger, Dong Man strongly believes that the culprit is Hee Soo. Meanwhile, Chief Han’s last struggle to hinder Dong Man’s investigation puts both Sun Ho and Dong Man in a dilemma.

It turns out that the head operator of the Zelkova Tree Foundation is also the one responsible for the illegal gambling ring, and Dong Man and Sun Ho finally stand face-to-face with the gang leader. Eventually, doubts surrounding the foundation get resolved one by one.

Sun Ho decides to quit school before he puts his last scheme into action. At the same time, Dong Man looks for a way to support Sun Ho in the best possible way. Years pass and everyone gathers again back at the university, hoping to meet the one whom they care about the most.