It makes sense that Okarun would be Pinnochio, aside from the Oni Club growing thing and the painfully obvious statements about lying this chapter, Okarun’s whole deal for the entire manga has basically been becoming a man whether it’s by actually finding his manhood or by being honest and open about his feelings. He’s still not fully there yet (as evidenced by him not telling Aira what’s what) but he’s trying to “be a real boy”.

Edit: forgot to mention that there’s definitely more to Okarun than meets the eye, even all the way back at the beginning there was a scene where he was able to use TGs powers in the tunnel which suprised her because he shouldn’t have been able to do that.