Ajitama

Combine Koikuchi Shoyu, Mirin, Sake, and Water in a small saucepan. Add Katsuobushi and Kombu.

Gently heat the marinade mixture over medium-low heat until it just begins to simmer. Remove from heat immediately and let it cool completely to room temperature, allowing the Katsuobushi and Kombu to infuse their flavors.

While the marinade cools, bring a separate pot of water to a rolling boil.