Thank you very much.
The higher the temperature of the water, the more astringent the tea is extracted.
The lower the temperature of the water, the less astringency is extracted and the more umami can be perceived, but it takes longer for the flavor to be extracted.
If you find 40°C too cold, try 70°C water for 1 minute 30 seconds. You will enjoy a different flavor.
Please enjoy Japanese tea!