Slice the bell peppers into long strips. Boil the soba in a pot of water for as long as directed on the package. Add the bell peppers to the pot halfway through the cooking time.

Once the soba has finished cooking, pour them into a colander, and rinse under cold water until the noodles are completely cold.

Place the soba in a bowl, and fill a ¼ cup measure ¾ of the way full with mirin, then fill it up the rest of the way with soy sauce. Pour this mixture over the noodles, as well as the sesame oil and sesame seeds. Taste, and add more soy sauce if you would like it to taste saltier. Mix well, and serve!