The Japan international is hoping to win over new manager Louis van Gaal in preseason.
He told manutd.com: "I think I have been training with focus every day. Pre-season is important to develop my physical strength. I learn a lot from training as we have a new manager with new tactics and a new formation. I am working to get myself into shape. It is good that I have been doing so without picking up any injuries.
"Some people say football is not very popular in the US but there are so many United fans here. It is nice to receive such warm support from them. It's a great environment to train in and we've had no rain. We can concentrate on training because of the great weather here."
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