(Taken from the wiki)
Touken Ranbu (刀剣乱舞) is an online web browser game by DMM and Nitroplus. Players assume the role of a Saniwa sage (審神者) who travels into the past to defeat evil forces that are trying to change the course of history. As a sage, you have the ability to breathe life into inanimate objects, including famous historical swords. Your duty is to bring these blades to life, create an army, and defeat the enemies!

You need a Japanese proxy to be able to play it, but some friendly users have provided ways to be able to play the game even if you're an outsider.

There is a wiki online which can help you with registering, starting up, and has translations for the game to help you play even if you don't know Japanese.
(Found here: http://touken-ranbu.wikia.com/wiki/Touken_Ranbu_Wiki)

So glad at least someone mentioned this game