Both.
Originally it was just @TeamYu, but that got suspended for resembling a spambot when replying to lots of Shenmue fans to notify them of the campaign. So it was replaced by @TeamYuNeedsYOU while appealing the suspension of the first account. When @TeamYu was reinstated both were kept going as an insurance policy against any future suspensions.
They are used slightly differently though. @TeamYuNeedsYOU retweets more, and favorites anything supportive of the campaign. @TeamYu retweets with more restraint, and favorites only the most noteable tweets such as those from celebrities or major websites.
I would suggest following both, as even the busier @TeamYuNeedsYOU won't flood your news feed too much outside of the Tweetathon, during which both accounts are very active.