Since we started business in 1972, we keep dealing with tuna as professional artisans.
Following features of "good tuna" are based on professionals and customer's opinion so far.

Each part of tuna (Otoro,Akami,Chutoro) is so-called stomach part, back part or tail part. However tuna are all different from one another and some tuna has less fat called "Garimaguro",which is thought as not so tasty one. So well balanced tuna is more valuable than unbalanced one.

Tuna is freezed immediately after they are caught and delivered to customers. However it is difficult to keep the quality because when it get frozen, the texture of tuna would be damaged. Thus it is said that the best quality tuna is raw ones.

The quality of farm-raised tuna is improved year by year, most of them are now raised in controlled clear sea water. So particular smell of farm-raised tuna is now decreased and more fat umami is included.Although those demerits are improved recently, still farm-raised tuna has few demerits on its texture and smell. So it is said wild tuna, which swims freely in the sea has much more quality than farm-raised one.

The best season of Bachimaguro is from September to the beggining of October.It's called "Fresh Bachi of east sea". It has enough fat and the redness is quite stable. However the taste is lighter compared to the others. Akami of India tuna is thicker and contain more umami.The most important thing for the taste is its sourness. In that point, Honmaguro is superior.

Honmaguro swims in both sea; Pacific Ocean and Atlantic Ocean.　Each of them spawn around the sea nearby equator and come up North. Finally, they reach the cold ocean and this is the best time to catch them. It is when they reach around Tsugaru Channel in Pacific Ocean and Boston/Canada open sea in Atlantic Ocean.

The taste possibly change according to how tuna artisans deal with it. The best way is to remove blood as soon as possible and soak into the ice water immediately. However it's not easy because of various reasons such as taking time to remove blood because tuna moves around. The the quality of tuna depends on the conditions like weather, the way they catch tuna and how to deal with it after catching it.

Processing Scheme

At last

I've talked about six points, but tuna is a fish with great individual differences.
When we wholesalers bid on a tuna, we judge it based on its shape, the subtle texture of its skin,
the thickness and color of its belly, the amount of fat when you cut off the tail,
and the feel of the red meat.
Ultimately, it comes down to a matter of intuition, based on our experience of what "this is good."
Every day, we listen to the voices of our customers, and as we repeatedly see and eat our food,
we instill that sensibility into our bodies.
Even with many years of experience, it is extremely difficult to distinguish tuna, which vary greatly from one another,
but this is where we feel the charm of tuna as a fish and the preciousness of nature's bounty.
The tuna that we win at auction is processed under strict hygiene control and delivered to our customers.