Hi there. This story, Kosuke and Saburo, concerns an original character and his friendship with an existing character in Sgt. Frog, so some explanation might be in order.
First of all the Kosuke here is the same character narrating my slightly longer Sgt. Frog story Fuyuki's Fury, which I encourage you to check out. Here however I take a better look at the character and wrote this to help develop him. As such it's a character driven story (the writing of which is also an experiment since character driven stories are something people don't often do) and the plot is not too much more than a normal day; the character interactions are what're important.
Second of all I would like to say that, while I'm sure many people might immediately discard this idea as being Mary Sue-ish (I know there're some out there) I would like to point out that I'm fully aware of what makes a Sue (which, contrary to the popular description, is more accurately a character for whom the plot bends over backwards to show in the best possible light) and am always keeping that easily thrown term in my mind. I tried as best I could to present this as well written and deep as I could.
Third, the choice of Saburo specifically is because his character is scarcely used in the main series, so he's basically free for the taking. Forgive anything that may seem out of character, but I tried extremely hard to portray him accurately. Not to mention the concept of Kosuke being a prodigy pre-dated an association with Saburo by about a day (I work quickly).
So yes, this was a bit of an experiment, but I think it's a successful one.