That' what I thought before... Before this chapter. Seeing Overhaul so damaged and Deku just appearing, It might be the time when Deku fights his definitive battle against Overhaul and when Deku is about to get beaten by a severly weakened Overhaul... Twice appears and stabs him on the face like "Sorry mate, I was ordered to clear up the mess I caused by taking you to the Villain aliance. We'll take good care of your bullets and that girl, though"
Chisaki is well designed by Hiroshiki, it'll be a waste to kill him right off his first fight.
I think Shiragaki can form an alliance easily wiith Chisaki if he promise to keep the Yakuza boss safe.