I think that Sonia killing Kazuichi would be extremelly boring and predictable, it wouldn't do justice for her character and she needs an actual motive to kill that has nothing to do with him and has everything to do with herself and her backstory
i don’t get the ‘bob is shy’ thing. he woke up out of a coma in an incinerator surrounded by mercenaries and immediately started trying to joke around w/ them and spill his entire life story