Is it true that Japanese professors wash their hair with water

It is. According to the information on the website of Hairdressing Station, Mr. Okahara said that it is important to pay attention to the method of washing hair with warm water, not to suddenly interrupt the use of shampoo, first of all, it is best to reduce the number of times you use shampoo to once every two days and then once every three days, and it is important to slowly reduce the scalp to get used to it in this way.