The romantic brawl between Kim Jae-joong and Ko Sung-hee in the most recent episode of action drama "Spy" is drawing a lot of interest from fans for their electrifying on-screen chemistry.

In the 12th episode that aired on Feb. 13, Kim Sun-woo played by Kim, who is a member of K-pop trio JYJ, comes close to blows with girlfriend Lee Yoon-jin enacted by Ko.

(IMTV/DN Contents/Studio Seven)

Reeling from the discovery that his lover is the titular spy of the series, who had been calculating attacks against him, Kim departs before turning back to interrogate Ko on the safety of his mother and her boss.

What ensues is a romantic and fierce spat between the couple.

The gripping action sequence, which was shot over four hours in Korea City Air Terminal in Seoul's Gangnam district, saw the actors good-naturedly helping each other within the narrow confines of the allotted bathroom space.

Insiders claim that Ko, who struggled to pull off a convincing rendition as an experienced combat-woman, was aided by the K-pop singer on set.

"They were able to convey the repressed romantic emotions of the action scene, culminating in an impressive scene," said a crew member about the pivotal scene.

The KBS2 drama, which took a break last week during the Lunar New Year festivities, airs two consecutive episodes every Friday at 9:30 p.m. and 11:10 p.m.

By Yoon Sarah (sarah356@heraldcorp.com)