For the Steamed Rice

• 2 1/4 cups uncooked Japanese short-grain white rice (3 rice cooker cups; 540 ml)
• 2 1/2 cups water (600 ml)

For the Onigiri

• Diamond Crystal kosher salt
• 3 sheets nori (dried laver seaweed)

For the Japanese Salted Salmon Filling (quick version)

• 1–2 fillet salmon
• Diamond Crystal kosher salt

For the Okaka Filling

• 1 packet katsuobushi (dried bonito flakes) (one packet is typically 3 g or 5 g)
• 1 Tbsp soy sauce

For the Tuna Mayo Filling

• 1 (5-ounce) can albacore tuna (preferably packed in olive oil)
• 2 Tbsp Japanese Kewpie mayonnaise
• 1/2 Tbsp soy sauce

For the Other Fillings

• 2 umeboshi (Japanese pickled plum)
• 2 sacs spicy salted pollock roe or cod roe (karashi mentaiko)
• shio kombu (prepared)
• furikake (rice seasoning)