Ven isn't too happy with the idea that Tidus deceived Terra into taking him somewhere so incredibly dangerous to get a weapon that Terra said he couldn't use, but he can understand the drive to try and do something to get his home back even if he tried a rather bad method to do it. And after Yuna disappeared, there was no way Ven wasn't going to try and make him feel better, whether it worked or not. Tidus feels a little "troubled" to Ven, but he thinks Tidus could be a good ally. If Terra could get over being used like that and become good friends with him, and Leon be good friends with him, then Ven thinks there's definitely something good there. They just need to talk more.