The CNBLUE leader is being accused of buying 400 million Won (~$342,564 USD) worth of stock and selling it for 600 million Won (~$513,846 USD) a week later. On July 16 of 2015, FNC Entertainment's stock rose from 20,800 Won (~$17.80 USD) a share to 27,000 Won (~$23.12 USD) a share following the signing of a popular celebrity, who's speculated to be Yoo Jae Suk.
It's being investigated when Yonghwa discovered the celebrity would be signing with the agency, and details of the stock deal are being thoroughly probed.