Please, wait until you are of age to try this. I honestly don't fell quite right about reccomending it to you, knowing you are underage.
If you are looking for a sweet sake, you may want to try Sayuri. It's pure Nigori sake. It is a bit strong, or it is for me. It has a sweeter taste than others I've tried. It goes really well with anything sweet, sour, or oily. I like it chilled, personally, but it's good either way. Here's a pic of the bottle for you:
It's really easy to get here. They sell it both at the asian food store and at World Market.
No offense to anyone or their parents, but I just have to say what I've heard described about parents letting their underaged children drink in there presence is NOT responsible parenting. Liquor laws are there for a reason. I know it's hard to believe but I waited until I was 21 until I touched anything and I was still responsible. I'm sorry, but all it boils down to is parents who are afraid to tell their kids "No." You can say that you'd do it one way or another, but if you had my parents, no you wouldn't. They are responsible parents. They honored the law and taught me responsibility. They answered any questions I had and told me how to drink responsibly once I was of age.
What these parents did was break the law. What kind of example does that set? That you can ignore the laws you don't like? They could be arrested for contributing to the delinquency of a minor. It doesn't matter that they are your parents. Ask the police, they don't care who is supplying you. The law says you have to be x years old to drink not you have to be x years old, unless you're drinking with your parents and then it's ok as long as you stay at home.
My family owned a service station for years. Trust me. I know my liquor laws. If they want to help you learn your limits, they can ask you over or come over once you are of age and do the same thing.