I'm sorry, I do not have an up-to-date list of mattress manufacturers in Japan. However, some popular Japanese mattress brands include:

• Simons
• Latexco
• Sealy
• Tempur-Pedic
• Sleep Number
• Serta
• Leggett & Platt
• King Koil
• Restonic
• Aireloom Please note that this list is not exhaustive and may not be completely accurate.