If you want more specifics, then I have them! Leon specially helped Anna out of school hours in order to accidentally find traces of the Spectrum on the Internet! His intervention led Alan and Clara into a trap. Leon imperceptibly switched the pill for Ben and Clara had to kill him! Leon tracked Ben down and could have installed video cameras, after which Mr. X came on stage! Mr. X confidently blackmails Clara, and Leon seems to have also become dependent on Mr. X, but Leon interacts very successfully. The events in the game reached their climax when Leon very skillfully and persistently seduced Clara and finally destroyed her marital morality! And that same morning, Clara was assigned to prepare a report on sex with Leon for a mysterious diary! How did the mysterious hosts find out about the events of the night? So is it proven that Leon is cooperating with Mr. X or not?No deduction method at all....see there is some X who want something from the hector company right and Clara is working for his mission as of now...yea maybe for his enjoyment he might be able to make her sleep with various men which Clara also dont mind and she is doing it too because she had to do it for the mission but he dont have to break her marriage as he has nothing to do with Alan or Clara or Leon or Anna personally.
X already told Leon and Clara that give him what he want then they can complete their own mission right? But here in this story you can completely see that X has the motive to seperate Clara and Alan (by setting Anna too with Alan, not just Clara)....that's why I said that there should be some story behind it and I think it should have been told while explaining Alan and Clara background...like they have some family feud or they harm some big gangster during their mission so they might be doing it to take revenge or something.
But as of now, Alan and Clara came from backgroud where they didn't harmed anyone and neither anyone from their family hurt anyone...so out of no where why is someone trying to destroy their marriage? Leon and his family also got Alan's father wealth then why to go to destroy Alan's marraige too ( If Leon is a con).