HAHAHA!!! Loved your post!
As an American of Asian descent who lived there for 2 years, I can say that as long as you make the effort (hell this applies for everyone, everywhere), most (if not all) Japanese will admire you for it. I got to know so many Caucasian expats who made no attempt to learn the language and by in large, they drew the most resentment from both the fellow expats and citizens.
Like you, what I lacked in language skills, my stomach more than made up for in size. However, the more time you spend there, you'll find that the former will improve and the latter will diminish (I just ate the traditional Japanese food and walked everywhere, and lost about 15 kilos). Also (if you're a guy), don't be too shocked when people reference your size to that of sumo wrestlers. This is not meant to be completely derogatory. The size factor aside, sumo wrestlers are well-regarded and your size will one of gentle ribbing--not meant to be hurtful. Related to this, do not--under any circumstance--be tempted to point out the relatively small size of Japanese men (physique--for those dirty minded). They consider this to be a deep insult!!
Just for your reference, most "upscale" restaurants don't require you to take off your shoes. Also, if you have tattoos, you may be prevented from joining a gym (an indirect rule to limit yakuza membership--or so I've been told).