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', as she does in the 2002 release of 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.
Versions of the game
The original Japanese version of the game was Kana Imouto, released in 1999. It did not include voice acting. G-Collections translated the game into English as Kana Little Sister in 2002.
In this version, Kana had brown hair and violet eyes. In the English translation, she addresses Taka as 'Bro' rather than 'Oniichan'.
In 2004, Kana Okaeri, a remake of Kana Imouto featuring voice acting and completely redesigned character art, was released in Japan. It was released in English in 2015.
There was also a 2010 PSP version that has never been released in English. It used the existing art from the 1999 game, and added new graphics as well as re-recording all of the dialogue with different voice actors.