D3vilL0rdM4ch1na The start seemed pretty good and I love the synopsis. I would watch out for doing this, “It is still a question that Keita Kuro asks himself every day. ” and not having a question or a question mark before this line. Also, you have a random period between rushing and to. You have a few random tense errors. I’m not a grammar expert but when I have two commas in one sentence I try to make sure the sentence flows on either side of the commas. Sort of like: A cat, of dubious origins, was bathing in the sun. There may be other times when you can use two commas in a sentence outside of a list, but I’m not sure what they are.
Another thing you may want to do is check the definition of some of the words you used. For instance, monolog is a long speech but you're using it with around 13 words split among two sentences. You should also go over your dialog and ask yourself; if I was talking to this person, at this point all of your characters are strangers to each other, would I really say that?
Finally, I think your pace may have been a bit fast. You’ve got two characters, that I’m guessing you introduced more in the two side chapters, and a trip from a house to a market and finally the guild. All of this is a bit fast and, personally, I wouldn’t label the chapters that you use to introduce your characters as side chapters, these chapters are too important for setting things up to be side chapters. When I see side chapters I think those are chapters I can read if I want too but I don’t have to read them to understand the story. Please keep writing!