From Charlie’s perspective: He took the joke Babe said about replacing him seriously. Which honestly tracks. Charlie consistently doesn’t have the highest self worth; and for a portion of the first season he was consistently reminded that Babe doesn’t really keep partners. So this combined with him seeing Babe with Willy online, and Babe not saying it to him. Leads to him being really suspicious and worried that Babe is really considering replacing him with the new guy. Charlie is blinded by his lack of self worth. He can picture Babe replacing him.

From Babes perspective: Two things, 1. Babe loves Charlie; like a lot. In his mind that’s not even a question. Him and Charlie are a team, a pair, (they are sold together lol), 2. Babe also cares a lot about racing, thus has his pride hurt because of losing to Willy; and being told it’s because of him being in a relationship that he’s not as good.

So in his mind; he not only wants to prove Willy wrong. That he is the undisputed number 1; he ALSO wants Charlie to prove Willy wrong; and wishes Charlie would put more into racing.

With all above in mind; him telling Charlie that he could replace him, was not only a joke. But also probably meant to be banter to motivate Charlie to do better. As Pavel said once (don’t remember where) Babe likes Charlie mad. Not only does he like in the bedroom lol. But in his eyes if Charlie is mad, it’ll probably be a motivation to do better.

Which makes sense from Babes perspective because he is definitely one to use his anger to push himself forward.

So, not only does he think anger is a good motive. He also thinks that him replacing Charlie isn’t ever gonna be a thing. It’s not even a question; that’s why he was comfortable joking about it. Babe is blinded by his perspective, and what he is sure of. He doesn’t see how Charlie could take his words seriously.

So with both perspectives in mind. Another thing my friend @azure-waves brought up that’s a really good point. Babe and Charlie both are likely to deal with issues on their own. Even if it should technically involve others; they will try to fix it by themselves. This is relevant because this might explain why Babe would hide meeting Willy from Charlie. On top of feeling comfortable that Willy is not ever gonna take Charlie’s place; he probably sees Willy as “his problem” that he can deal with on his own. To him, beating Willy solves the issue of his hurt pride, might make Willy give up, and or whatever the heck else. But Charlie doesn’t need to worry about it in his eyes. I’m not saying that justifies him hiding stuff to the audience, but it might make sense to him, with the way he is used to dealing with things on his own.

As for Charlie, also being a person who deals with things on his own. He is suspicious of Babe. So he keeps his cards close to his chest as he watches Babe to see if he really does have something going on with Willy.

[Id. Digital sketch of Zura, Takasugi, Gintoki and Tatsuma sitting on a deck fishing. Gintoki pulled out a boot Tatsuma's catching with a net. They're having a lot of fun. End Id.]

「There’s a vehicle here without a driver at the side of the road.

Are they in trouble?」