Hm, that makes sense. "Cooperation" is a good description of the relationship they share right now.
Still hype about Amon's return >_<
Indeed. That's why I love this chapter because Sasaki was afraid to disappear, so he didn't want to get his power involved. Last chapter, he was convinced that the ghoul in him was a real good guy, so he didn't mind giving up but still going to get erased. Then Kaneki in this arc was showing his true color and that's fear. It remind me of his first centipede transformation, where he fought Amon first time and then broke down of not eating anymore, but here, it's his child self, symbol of purity. Someone you will feel sorry for, especially as a kid. So Sasaki now understands him, so he will help him.
The fact he lied to Arima for the first time is a development. He was fine with his family, good or bad, so he's cooperating with them and pretty much follow them since he is most loyal to them, especially Arima. He may have his own agenda, but he still loyal to him like doing this and that and be truthful. It's not that he never lied (until now), rather he never was pushed to say what's troubling him or his real plan. Here is the first time, which tempered his loyal trust with Arima, meaning he's moving further to be independent and follow his own way. It's growing and this is the startup. Something tells me Kaneki/Sasaki will soon have his own team.