Actor Hong Jong Hyun opened up about his 'Moon Lovers: Scarlet Heart Ryeo' co-star IU in an interview TV Report on November 9.

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Hong Jong Hyun was asked about his chemistry with IU, and he answered, "We started working together in the middle of the series. I listened to IU's music a lot before that. I knew she wrote and composed her own songs, and I always thought of her as a sensitive person," adding that he was right about his impression of her.

He added, "Because she's someone who does music, she was able to express sensitive feelings well. She was also mature for her age. She looks very small, thin, feminine, and like she'd get tired soon, but she's not like that at all. I don't know if it's because her stamina's good or if she just withstood it, but she has more strength than an average man. She held her form from beginning to end."

Hong Jong Hyun concluded, "Though acting isn't her original career and she's still gaining experience, she was extremely professional."