DESCRIPTION:
***Please read the description.
Original title: 【初音ミク・ＧＵＭＩ】秘密ノ金魚【-MASA Works DESIGN-】
by MASA (まさ)

***EDIT 2: I've been getting a few harsh comments from a certain somebody who will remain unnamed (unless they choose to reveal themselves yet again). This translation is, admittedly, not 100% accurate, but I think most of you don't mind, considering this person is the only one to complain, so I will leave this up.
They linked me this translation, so if you are dissatisfied with mine, look at this one: http://vocaloidlyrics.wikia.com/wiki/%E7%A7%98%E5%AF%86%E3%83%8E%E9%87%91%E9%AD%9A_%28Himitsu_no_Kingyo%29
I don't do translations anymore, mainly due laziness. Please do not subscribe to me for translations, though I do appreciate subscriptions.
This person also refutes that no such "goldfish in a box" tradition exists in Japan. I can't find any articles or anything proving them wrong in their denial of the tradition, so perhaps they're right. (They suggested that apparently "goldfish" is not a metaphor for "corpse", but is instead a metaphor for "vagina". Take that info as you will.)

As to why the translation is "wrong", I translated it very literally, line by line, and as a result, I am thought to have used Google Translate. I did not use Google Translate. I used my own (very little) knowledge of basic Japanese and Jisho, an online dictionary. I simply prefer literal translations that stick as close to what is shown on the screen as possible. That's just my opinion, though. For this, I have been labelled as an "unrecommended translator".
... I won't argue this. I translated merely for anyone too impatient to wait for someone better to translate it, and also as a way to practice mimicking subtitles.
So yes, you-know-who, I am admitting that I am not a fluent Japanese speaker, and that really I only know a few words and how to recognize past-tense. (Which I don't think I knew how to do when I did this translation.) Are you pleased? ( ͡° ͜ʖ ͡°) Please stop leaving harsh comments, for I am aware of my inaccuracies, and my "mistranslation" is meant merely as a last resort more than it is meant to be "harmful" to MASA.
My apologies to MASA if he is, in fact, offended by my literal translation.

"Greetings, I'm MASA.

"That girl didn't show the treasure to people
"But the girl's best friend was the only one it was shown to
"That is the trivial promise between best friends.

"'SUCH GOOD FRIENDS'


"□-MASA Works DESIGN-□

"□Music/Video/Art by MASA□"

Edit: Wherever it says "the secret of the goldfish" it should say "the secret goldfish" because I dun goofed.
I'm a big fan of MASA's works, so when he released this yesterday, I nearly went ballistic. Maybe someone's already beaten me to this, or maybe someone else will come along and translate this better than me, but here's my attempt.

Check out the original upload here and support MASA!
https://www.youtube.com/watch?v=v6_O83RMPFU

Translated and subtitled by Noelle McHenry (me).
I did not get permission for this translation or subtitling, so if MASA wants me to take this down, I will (it would suck, though).

-------------
English lyrics: http://pastebin.com/uTtADNVS
Romaji lyrics: http://pastebin.com/vxLZv86C