Japanese ponzu sauce is a condiment and ingredient based on soy sauce with both a citrus and savory flavor. You can make your own ponzu rather than seeking it out at the grocery store or international market. Ponzu has the umami element as well as sweet, salt, and sour flavor elements. Ponzu can be used in many different ways. It's often used as a condiment or dipping sauce. It can be used as a marinade and may serve both of those purposes for chicken yakitori. Just keep in mind that you should discard the marinade used for the raw chicken and only serve untouched ponzu as the dipping sauce.