1) Download and install ''JPEXS Free Flash Decompiler'' (go to page 172 where Icevail taught me how to use it), then download ''Notepad++''
2) When you have the swf which you want to translate (there are japanese texts both in the main file of the game and in the ''subs'' files) opened at JPEXS you'll notice that the script is divided in ''Timelines''. When you find one with the ''good stuff'' in japanese, press ''Edit Actionscript'' (seriously, go to page 172 and read the instructions).
3) Then, press 'Edit Actionscript', right click and Select All, copy, and paste the full timeline in Notepad++. Open a new project in Notepad ++ and Repeat this action with all the timelines that have dialogue in japanese, each one in a different tab.
4) Okay, now you will select the text in japanese, put it in the translator (which is a terrible translating from Japanese so you'll have to work hard), then you have to select what you want to translate and press Ctrl+H, and replace below the japanese text with the translation pressing ''Replace All in All Opened Documents''. Otherwise, you'll have to translate the same texts over and over again.
5) When you finish with the timeline, do right click and select all, copy and go to the same timeline in JPEXS, click Edit Actionscript, select all, Delete, and paste. Then save (first below, then on top left), and go to check the game.
Take care not to erase anything but the japanese dialogue, things like >< '' <br> are part of the game code.
I hope I've helped. My english is imperfect, sorry about that.