During WW2 d-day landings it is said that condoms provided for British soldiers were marked "XXL - British troops only". This was a rather obvious morale-boosting initiative. Quite what the Americans thought to it I have no idea.
Anyway the point is that Japanese condoms are different from American / European ones. I've heard some claim that they are, how do I put this delicately, on the SMALL side.
Others contend the Japanese product is thinner and superior. Either way it is probably better to stick to the tried and tested.
Toiletries and Medical Supplies:
most toilets do not have hand towels and many do not have hand dryers. In addition, many resturants do not have napkins.
Bring a handkerchief or small hand towel to carry with you. It will save you from wiping your hands on your sleeves and pants
Miscellaneous: Pack your swimsuit. When Tokyo just gets too much, when the crowds begin to press in on you, when the stress of city life begins to tell - just do what the people of Tokyo do and head for an aquatic theme park. Splash in the water or relax beside the pool. The only problem is that the day you decide to go - half of Tokyo will have made the same decision!