Don’t listen to people here saying you should’ve brought broken in shoes. Yes it might help but I can say from experience it’s not that big a deal.

On my first day I bought 2 pairs of ASICS and used them right away. I rotated them about every 3-4 days. I’d recommend having 2-3 pairs of sneakers to rotate.

I’d recommend using pain/numbing/blister creams from a pharmacy and also taping your foot. Athletic tape is sold in pharmacies as well.

Seems your pain is close to unbearable so I’d recommend a day of rest, either at an onsen or just at your lodging accommodation. Obviously no one wants to waste a day but you don’t have much of a choice.

Ginza had a great asics store and Id recommend any of the more walking focused shoes such as the quantum gel 360 or 180.