Tomb Raider Japanese Language DLC - トゥーム・レイダー日本語音声/字幕 増加パッチ
This is the DLC pack you can get from Steam for an additional 30 USD/EUR.
Installation instructions: 1. Copy all downloaded files to the game main folder. (Backup the movies folder if you want to change it back to English later on) 2. Edit .ini file in game folder to change language. (Mine's Skidrow.ini) - Note the # tag. # Language = "English" to Language = "Japanese" 3. Play.
This torrent was originally available on piratebay, but the page has 404'd, I could only grab the file using a magnet url from Google's cache.