It appears that malicious comments about actress Jin Se Yeon are at a peak, especially after Kim Hyun Joong's ex-girlfriend's recent letter. 

Just yesterday, Ms. Choi had released a letter detailing the various times she's allegedly caught her ex-boyfriend Kim Hyun Joong cheating on her. Ms. Choi specifically mentioned walking in on Kim Hyun Joong and a female celebrity 'J' in bed together. And ever since then, malicious speculations sprung up with netizens guessing that 'J' may be Jin Se Yeon, especially since the actress and Kim Hyun Joong have been in a drama together before. 

The actress even spoke out directly regarding this matter by tweeting, "It's not me, so please don't speak so rashly like that."

Jin Se Yeon's company 'Early Bird Ent' also told media outlets, "Last year, we had sued the people involved in hate comments towards Jin Se Yeon. Since the commentors were middle and high school students, the matter was tied over with volunteer work. But malicious comments have recently come up again. This time around, the number of comments are very high, so we are considering taking legal action."