Followers of Kim Min Suk were surprised after the actor showed his romantic side in an Instagram post on Monday.

According to Soompi, the actor uploaded a selca with child actress Shin Rin Ah and captioned the post with a sweet message. "Hayeon, the driving force of my life these days," he said.

Kim Min Suk and Shin Rin Ah currently appear in "Defendant" as Lee Sung Kyu and Hayeon, respectively. The 27-year-old actor plays the mysterious role of an ex-convict who looks after Hayeon after his father was convicted for alleged murder.

On the Feb. 20 episode of "Defendant," Lee Sung Kyu's past was slowly revealed, exposing how he took part in Cha Min Ho's (Um Ki Joon) plan to ruin the life of Park Jung Woo (Ji Sung).

After he was acquitted of assault, Lee Sung Kyu has been the protector of Hayeon while Park Jung Woo tries to recall who framed him for the murder of his wife.

The SBS legal thriller has been leading the Monday-Tuesday late night timeslot. Korea Herald cited "Defendant" earned a viewership rating of 25.2 percent in Seoul households and an overall rating of 22.2 percent.

Given the figures, the Ji Sung starrer furthers its lead against contenders "Rebel: Thief Who Stole The People" and "Hwarang: The Beginning" with 10.6 and 7.7 viewership ratings.

Aside from its gripping and twist-filled plot, "Defendant" has been receiving good reviews for its lineup. Particularly, Ji Sung is winning the sympathy of the viewers for portraying the unfortunate fate of Park Jung Woo.

In the upcoming episodes of "Defendant," the conflict between Park Jung Woo and Cha Min Ho will continue inside the prison. On the other hand, Lee Sung Kyu will try to guard Hayeon from the villainous plans of Cha Min Ho.

Catch "Defendant" every Monday and Tuesday at 10:00 p.m. on SBS.