both series have:

- childhood friends turn into lovers
- one in the showbizz and the other one has a job out of the spotlight
- their relationship is causing trouble with fans, sponsers etc.
- both series have green flags in them

Both series are sweet bl's about the struggles in showbizz. But in 25 Ji, Akasake de both main characters are actors and in city of stars only one of them is an actor. The biggest similar thing is that they are both BIG GREEN flags. <3