Tunnel (2017)

In 1986, Park Gwang Ho works as an excellent and enthusiastic detective. His life changes when he’s pursuing leads in a serial homicide case and then passes through a time portal, which transports him to present day Seoul. He meets a new partner Kim Sun Jae, an elite detective who happens to be a bit eccentric, but is one highly skilled investigator. The detective duo will also find help in psychology professor, Shin Jae Yi. (Source: MyDramaList)