Takuwan (takuan) is pickled daikon, a type of tsukemono, or preserved vegetable. In our house, we called tsukemono, “ko-ko.” Mom would serve just a tiny portion of ko-ko, nestled up against the rice, with every dinner. Here’s a recipe for this ko-ko that is usually bright yellow, but if you are wary of food coloring, you are welcome to leave it out.