>>21562781
>>21562802
They don't trim the crust, it's a type of crustless bread called Shokupan.

We have something similar in Argentina and Uruguay called miga (breadcrumb) sandwiches.

Basically the bread is rolled repeatedly and then baked in huge metal molds creating a huge spongy bread block with a very thin crumb (which is stripped away) and then the interior is sliced and sold as a crumbless bread type (miga bread).

Japanese shokupan uses milk to create the spongy texture and thin crust (rather than the giant molds of miga bread) but it's basically two ways to achieve a similar result. ("crustless" spongy bread)