We need to get more information about Leon! So far we've seen how brazenly Leon broke into Gunnar's! Everyone is afraid of Gunnar, and Leon turns out to be cooler than Gunnar! If Leon shows up like that at Mr. Brown's, then I'll believe your version. But still, Leon can't call himself.It's done by an assistant or an artificial intelligence! I'm determined to wait...
Does he call himself or just receive texts? Remember he did something with the computers early on as you stated, that he made Ana not say anything about. Could be a program to send the messages or calls from/through Alan's computer to frame Alan if they get traced back. Set Alan up to take the fall by making it seem like he is X. Makes Clara leave him since she will think he's behind all the things she has to do from X, along with all the other things Leon is doing in person, as well as implicate him in being the mole. I mean it's a typical plotline but so far most of this story has been. Nerdy, little dick, impotent MC who can't satisfy his hot wife. Assistant who loves and is trying to make the MC fall in love with her. Macho big dick rival/bully from the past who has sex with and tries to/is stealing the MC's wife. Hot wife who appears to be strong, intelligent and faithful, but truly isn't, cheats on MC and has moral dilemma about it while being corrupted (usually when people see she isn't what she was made out to be). All of that is typical in NTR game tropes/storyline. Dev added X as a means for the corruption and to add mystery to the story. How many people would still be as interested if it was Leon openly trying to corrupt her(showing his true colors). Also with him doing it openly it shows how truly dumb Clara would have to be to fall for it all. So yea it makes sense that X is Leon doing another typical villain trying to frame the MC to get the hot wife/prize at the end.
Take that as you will but that is my take on this story. Making X someone not yet introduced or someone from the past could still be possible but also requires ALOT more work from the dev. It's not much of a mystery story if there are not clues as to the mystery Villain. The point of mystery is to figure out who that person is, without clues and just making a big reveal at the end can be a shocker story but makes the entire mystery rather pointless other than to keep people baited in until the end. Those usually aren't very popular unless the storyline is very compelling to keep people's attention. I mean as an NTR story with corruption a lot of people don't really care about the story and only want sex scenes and MC getting cucked/screwed over so they'll stay as long as those requirements are met. Some people who were here for the storyline or wanting to try the save the marriage path have already left, others are watching and waiting for the end. Again I'll state this is my take on things as I'm more of a story person than lewds/sex scenes/fap material type. There are better games/stories out there for those as the renders I've seen are average(Clara being the best in this story so far).