"Everything he said pretty much not say anything clear about their motive of helping them"
That's true. that's most probably because he wants to keep his cards close to his chest. He wants to take it nice and easy,at his own pace. That's just the type of character he is.
It is also true that the way sachi is now, she won't believe anything he says anyway. so he needs to first calm her down, and help her become rational normal person.
"? he have enough time to react"
i don't think so,nope.
"Just see, both time only when the side kick guy start talking, its work. The detective's words is just not work at all. It either actually have a dead wish that will reveal later. Or he just simple go retard for drama effect"
he is not afraid of sachi,so he obv does not have a death wish. imo she reminds him of himself when he was younger, but that's just my hypothesis.
and he is not a retard either. he has been acting pretty much how his type of characters, the smug super-intelligent or detective types, do.