Rainfall could top 1000mm in some areas; identical to that which claimed scores of lives in the Shizuoka and the Kanto region in 1958.
The weather system is also expected to lead to 13m waves on several islands off the Japanese mainland.
Local officials and forecasters have warned locals and touring rugby fans to keep a close eye on latest forecasts, get up to speed with evacuation plans and avoid going outdoors.
Hagibis has also led to the cancellation of more than 16000 flights – domestic and international.
Many train services will also be scrapped because of the weather, including almost all rail services in the greater Tokyo area from late afternoon.
Theme parks including Tokyo Disneyland the Tokyo DisneySea have closed their doors today.
The Japanese Government has increased the number of English, Chinese and Korean-speaking interpreters on tourism information lines in a bid to ensure visitors are aware of the risks and what to do when the typhoon hits.
An article on NHK – the Japan Broadcaster Corporation – has stated weather damage could lead to disruptions of Japan's telecommunications infrastructure.
Mobile and landline operators had extra crews on hand for damage repair.
"The three mobile carriers are offering disaster message board services on the internet. They are also running a service allowing customers to post voice messages on an app, which will then deliver the messages to specified mobile phones," NHK reported.
"Fixed line carrier NTT East is also offering a disaster emergency voice message dial service. If customers dial 171 from mobile or conventional phones, they can leave messages for other users, who can then retrieve the messages by dialling 171 and inputting their numbers."
On Thursday, World Rugby announced the decision to cancel the All Blacks/Italy and England/France clashes because of weather concerns.
More cancellations could be made tomorrow, including potentially the crunch Japan/Scotland match.
NHK has warned locals and travellers of potential flooding risks.
"Underpasses below railways and elevated roads are especially vulnerable to flooding. Fatal accidents have occurred in the past due to cars entering underpasses unaware of flooding," it reported.
"When a car is flooded up to around 30 centimetres, its engine will stop, and at 50 centimetres, the vehicle may float and get washed away.
"It is best not to go outside. But people with pressing needs to drive are advised to pull over when visibility is poor and keep their cars parked at safe locations until rain and wind subside.
"Underground locations also pose a hazard, as people there may not notice heavy rain and floods outside. Once flooding begins, the force of descending water makes it difficult for people to go up stairs. Power outages make elevators useless.
"Underground doors become difficult to open when water on the other side reaches a height of 30 centimetres.
"In 1999, a person was killed in a submerged underground arcade near JR Hakata Station in Fukuoka City, western Japan. Another died in a flooded basement of a house in Tokyo.
"People should avoid going underground during heavy rain, and evacuate quickly when there's any sign of flooding."
NHK has also advised pedestrians "to walk in pairs or larger groups, and use umbrellas or sticks to check for possible hazards on the ground"; those hazards include drain covers which may have been washed away.
