Well, let me see...
The Companion file is technically a mini Japanese-English dictionary. It was started when Konekochan used to get lost in my writings cuz she forgot words and I only translate at the first appearance. After that, well, you're pretty much on your own when reading.
Forgive me, I like to keep my fics as authentic as possible, so the characters will speak Japanese frequently.
Version two of the Companion file was quite unweildly, so I'm restricting it to just the commonly used phrases, as well as some notes on Japanese culture and language that you need to know if you're really going to follow me. Don't be afraid or anything, you can still understand the story, but a full understanding involves this. ^_^ Think about it this way -- you'll be learning something. O.O
If you have any questions, or I've missed something, please feel free to email me. I am, afterall, still just a student of the language, and it's not uncommon for me to have things wrong.

Good luck and cherry blossoms

-Inseiko

alright, that's enough, now on with the mini-Japanese lesson!

(1) Common Words/Phrases
(2) Language/Cultural Notes

Commonly Used Words and Phrases:

Ano -- "um" or "uh..." it's an interjection.
    Ano ne -- usually translated to "well then"

Arigatou -- Thank you
    (Domo) Arigatou Gozaimasu -- Thank you very much. Also the more polite form
    Arigatou Gozaimashita -- Past tense of Thank you. (I know, sounds weird) Used for when you're thanking someone for something they've done in the past

Baka -- fool/idiot
    Bakayarou -- often translated as "jerk" or "bastard", derogatory in any case

Chibi -- small, or little. The word is actually condescending, used for children

Chikyuu -- Earth

Daijoubu -- Alright
    Daijoubuka -- Are you alright?

Demo -- but

Ecchi / Etchi -- Lecherous person

Gomen -- (I'm) Sorry
    Gomen nasai -- more polite form of the above

Hai -- yes

Hentai -- Pervert, perverted, pornographic.

Hontou -- for real, really

Iie / iya -- no

Kawaii -- cute

Ki (also chi) -- Internal Strength

Kisama -- a derogatory way of refuring to someone as, simply, "you" this isn't a light derogatory either, it's actually very mean.

Konnichiwa -- Hello, Good afternoon

Kombanwa -- Good Evening

Maa -- "well..." (interjection)

Matte -- wait (imperative, 'te form of Machimasu)
    Chotto matte -- Wait a moment
    Chotto matte kudasai -- Wait a moment please

Minna / Min'na -- Everyone

Mirai -- Future

Nandemo nai -- (it's) Nothing

Nani / Nan -- What

Ohaiyou -- Good morning

Sayounara -- Good-bye

Shine -- Die (imperative) pronounced Shi-nay.

Shounen -- young boy

Shoujo -- young girl

Sugoi -- (that's) Great

Sumimasen -- I'm sorry / Excuse me

Uchuu -- Outer Space

Yaa -- informal greeting, like "Hi"
 

Language/Cultural Notes:

                -- Desu, and all forms therof
                -- references to people (chan/kun/san/sama)
                -- references to yourself
                -- family members
                -- random cultural notes

Desu

*Desu is a polite form. Simple and true. It basically means 'I'm being polite here' but there's no possible way to translate the word itself. To use "Watashi wa Inseiko" and "Watashi wa Inseiko desu" as examples, both of them mean "I am Inseiko" it's just that the latter is more polite than the former.
It is also used as a tense marker. "Watashi wa Inseiko desu" and "Watashi wa Inseiko deshita" both use a form of desu, but the first one means "I am Inseiko" while the latter means "I was Inseiko"
Another use for desu is to make the sentence negative, while still being polite about it. " Watashi wa Inseiko dewa arimasen" means "I am not Inseiko" and "Watashi wa Inseiko dewa arimasen deshita" means "I was not Inseiko"
Ehhh.... it sounds more complicated than it is.
It's very uncommon for me to use a full sentence with desu in it during a fic. Usually it's just for introductions and stuff. "Boku wa Xellos desu" or "Watashi wa Lina desu" But I like to be thorough, and the note on making the sentence negative applies to a Slayers fic with Xellos so...

References to People

The following are suffixes that, to put it simply, convey how the speaker feels about the person.

* -chan
This is a friendship term. It is used only for when you are familiar with the person. It's used for younger children as well.
When using it for a friend, it's proper to only use it for girls.

* -kun
This is the same as 'chan, however, it is proper to only use it for boys.
This is also the way teachers refur to students

'chan and 'kun are a good way to differentiate character's gender. Hence Ranma-chan and Ranma-kun refur to the female/male counterparts.

* -san
This is used as a form of respect. This is most often translated as Mr. or Ms. etc.
It's also gender neutral, and can be used no matter what

* -sama
A higher form of respect than 'san. This is reserved for people who are to be revered, like royalty and the likes. Often it is translated to 'Lord' or 'Lady'

* -sempai
An Elder or Upperclassmen. This is used for someone in the same school as you, but who's at a higher grade. Basically, it's for people who came before you.

* -sensei
A teacher. Affixed to a teacher or master. It is also used to refur to those who have mastered their profession. Lawyers and doctors, if I'm not mistaken, are to be refured to this way.

References to Oneself

There are three ways for one to refer to themselves.

* Watashi
This is the polite way to refer to yourself, it's gender neutral, but there is no alternative for girls.

* Boku
Not as polite as Watashi, but still polite. This is used only for boys, but tomboys are known to use it.

* Ore
A familiar way for boys to refur to themselves. It's not polite, but not horribly rude either far as I can tell.

Family Members

This used to be a part of the common words/phrases etc, but I've split it into it's own section.

Otousan -- Father
Okaasan -- Mother
Oniisan -- Elder Brother
Oneesan - Elder Sister
Ojiisan -- Grandfather
Obaasan -- Grandmother

All of these are the polite form, and can have the O dropped from the beginning to make it less so.
Also, these are moreoften used to refur to someone elses father mother etc, but in anime, we usually hear these forms. I couldn't tell you why, really. But in order to stay true to anime, this is what I use.
Note: Ojiisan should not be confused with ojisama, for the latter means 'prince'

Random Culteral Notes:

Okay, I finally thought of something to put in here.
This has to do with the Weiss Kreuz story "Ima" and a sappy scene with Riva and Brad that I wrote esp. for Teychan. (not posted on this site) It has to do with Riva's Apartment.
I gave Riva a very small apartment, which is typical in Japan. Especially since she's living on her own, she wouldn't be able to afford anything bigger. It's a two-room apartment. But it's more like a small room + a large closet.
In Japan to conserve space the main room in an apartment like this acts as *everything.* During the day the table is the central focus. There is a small kitchenette to the side. (If you watch the movie Perfect Blue, Mimarin's apartment is kind of like this - except that she has her bed out all the time) At night, the table is pushed to the side and the bed/futon is pulled from a closet. The other room is the bathroom. Not much more I have to say about that, except that in Japan (all Asian countries actually) the whole room is waterproofed. Custom in Japan dictates that everyone uses the same bathwater. It sounds gross, I know. But what's done is you shower *outside* of the bathtub on the floor, and then get into the bath to relax. You don't actually bathe in the bathtub. (watch any anime bath scene - you'll see. Particularily, Dirty Pair Flash Mission Two has a scene that illustrates this perfectly, as does an episode of Black Heaven. So does volume 7 of the Mahou Tsukai Tai manga -- I might scan that to make up for my lousy description) Ehtou... let's see... what else can I say? Parents usually bathe with younger children (again, see Black Heaven, also an episode of Cyber Team in Akihabara that alludes to it. I can't remember which one) but that doesn't apply here. Oh yeah, when in the bathtub, put your hair up. It's rude not to. Okay, I think that's it. Any questions, go ahead and email me. ^_^