Again a mistranslation.... In the RAWS Shunsui said he was going to use it when Stark uses his real power (The wolves) remember when Shunsui was saying that Stark was a bad liar? heres the
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With Love and Rose I dont think they were gonna use bankai and if they were then Shunsui saved Kubo the hassle of releasing some more bankais... But thats up to speculation I just think that Stark was gonna take them out if not for Shunsui. They were very beaten up and would have been slowed down heaps.
I dont know in the panel it looks like a gun the shape and everything, and I think that Shunsui just didnt give him any space to use the guns and forced him into CQC.
Yeah Zaraki is definitely a powerhouse, and Shunsui is making full use of that potential of his... I think the vadenreich are gonna have a nice surprise. The gotei still have powerhouses left with them Ichigo, Zaraki, Shunsui, Ukitake (Fully healed Kubo said it would happen), Shinji and Mayuri (His inventions and work is going to help SS a lot I think). Urahara , Isshin and Yorouichi are there as well.