Some people asked about surfing lessons. I can't recommend one place over another, since I learned to surf in San Diego. Having been through surf lessons, I'll say they are helpful but not all lessons are created equal. Usually an instructor will take the a big group of students out on long, foam boards for several minutes because it's easy (for the instructor). However, learning to stand up on a 12 ft long foam boat takes a few minutes, while learning to surf on a real surfboard can take about 3 months. So while entertaining delusions of grandeur (see above picture), the reality is pictured below.
That being said, one surf school that my sister found is Hawaiian Fire surf school (click on link in name). Basically, it is a bunch of Fire Fighters (yes, the instructors are Open Water rescue, EMT, and CPR certified who run into burning buildings for a living) that also teach surfing. They teach at a beach away from the Waikiki crowds with small waves in small groups. So the lessons are generally safer and you get more out of it. Now expectations are more realistic, like the picture below.
So check out their website, location, times, prices, and reviews. They do individual and group lessons depending on how much time you have, how many people in the group, and how much you want to spend. And by the way, they have experience teaching tourists from Japan and their website is in English and Japanese.