Both dramas have a ML who is sickly, weak but highly intelligent and masterminds of everything, at the same time somewhat charismatic. Both FL are good at fighting and becomes intangle with ML due to some past who needs to be investigated. Both have similar humour and quirks, but The Moon Brightens for You is more comedy than Love in Between.

Same vibes, school bullying with a murder investigation on the background. Both involve foundations and shady business between the board members and such. If you like one, you will like the other.

Same Writer with Male Lead characters with similar professions: The two are swindlers with a knack to impersonate everyone and everything they set their minds to. Both FL are civil servants too (In MFC, she is a cop and in 38TF she is a member of Tax Collection Bureau)

Sometimes, Yang Jang Kook reminds me a lot of Yang Jeong Do.