Bring the soup up to a boil briefly and skim any scum. Hold here for 5-10 minutes, or until the scum subsides.

Reduce the heat back down to below a simmer (around 88 °C), and hold for 5 hours.

Add onion 1 pc, garlic 10 pcs, ginger 25 g, niboshi 20 g and kombu 20 g. Cook for an additional 45 minutes.

In the last 10 minutes, add the bonito flakes (katsuobushi 20 g) and steep.

Strain the soup and hold it until needed.