5:41 “a combination of large utilitarian vessels” displays an absurdly useless “art piece” pot split wide open and half melted. Not utilitarian or beautiful. It’s a pot lost to zealous adherence to destructively poor firing technique.
The late Heian period is not 850Ad. It is about 250 years later! Heian Period 794 to 1185.Also, your pronunciation of the Japanese is not good."Fukai Prefecture",it's Fukui Prefecture.