Well, people are wanting a Kaku side-story, so I thought.. why not do one myself?
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(It takes place right after Zoro's beaten him, got his key and left.)
Kaku lay on the ground for a while, contemplating what he had just experienced and thinking about his purpose. To be honest, he wasn't really bad, he was just a soldier following orders, he was just a man doing his job. He continued to think about this as the marine doctors fixed him up, when he suddenly sat up, and went to the window.
''That kid...Straw-Hat...he's fighting Lucci....''
He flopped down onto a chair as he saw this.
''Why would he do something like that? Why would he fight someone who is stronger than him? Is it stupidity, or.....bravery?''
He walked out of the infirmary, encountering Spandam along the way, who looked livid.
''KAKU! You had your key taken! Hunt down that guy that took it from you! This is an ord-''
''RANKYAKU!'' Yes, Kaku had just attacked Spandam, and was standing over him with a pissed-off look on his face. ''I'm sick of taking orders. From now on, I choose my own path. You can take your 'justice' and stick it up your ass.''
He walked past Spandam, standing on him as he did so, down the stairs, and out of the tower. A few marines tried to stop him, but he knocked them down, saying to one of them before he left, ''The truth is kept secret.''
Kaku came out of the tower and headed to the Sea Train. He told the driver to go back to Water 7 and he complied, riding the train off into the sunset.
(I might do more if I get comments. I know it's short, but I promise the next one will be longer.)