I took it more like Kage having an inferiority complex, leading him to undermine his contributions to Bojji's dream. So he lies to Oyabu because he either doesn't want to admit his feelings of worthlessness or he doesn't want Oyabu to know how he really feels. At least that's how I read it based on how he behaved in early chapters, but you're right that it could be him finally maturing into someone more shrewd which would also be pretty cool.So many layers here... I think Kage is more shrewd than he sounds, lying to Oyabu about his motives to try to get Oyabu to be their ally. But then I think Kage is still being a bit naive about the risk of having Oyabu around, not believing Oyabu would really just kill them in cold blood. But what's for sure is that they both understand the staggering potential Bojji has. It's getting to the psychological complexity of a FKMT manga lol.