Once again, spoilers lurk beyond this point, especially in the story-specific sections. You've been warned.
General notes
First off, some notes on Japanese culture. Taka and Kana are Japanese characters, and I wanted to stay true to that.
Kana is Taka's imouto (little sister). Conversely, Taka is Kana's oniichan (older brother). I've used these terms in these fanfics on occasion.
I drew the line at having Kana actually call Taka 'Oniichan', though. It just didn't feel right. And so she calls him 'Bro', just as in the game, though I think it makes her sound like a teenage African-American girl. =Þ
"–Chan? –Kun? –San?" The Japanese language uses affixes to indicate the speaker's relationship to the person being addressed. These are attached after the person's surname or, if you're close enough, their first name.
–san is the simplest polite way to address someone of either gender (roughly equivalent to 'Miss', 'Ms', 'Mister', etc). For example, Yuta-san, Miki-san.
–kun is how you'd address a male friend or a young boy. For example, Ikuro-kun, Masa-kun.
–chan is how you'd address a close female friend or a young girl. It's an endearment that translates to 'darling' or 'little one'. For example, Yumi-chan, in the first sense, or Kana-chan, in the second.
These rules aren't hard and fast (you can address a female friend with –kun if you're not that close, and girlfriends often call their boyfriends –chan), but they work well enough in the context of these stories.