I just had a stroke of genius. Go to a fish market (I know Toyosu lets us small people in) and go to one of the restaurants there. Freshness guaranteed.
Are you in Tokyo?
I went to nakizakana once and it was good.
https://maps.app.goo.gl/paSyD7p1GfupxW8V9?g_st=acI know Uokin is a very standard izakaya branch there.
Ozeki is a grocery branch that does fresh fish (might depend on the store)