Where to buy osechi?

I wonder it's possible to osechi bento box or walk in to restaurant with osechi without reservation? If so, is it usually available only on the day? For reference I will be at Hiroshima city on the NY day.

Thank you

Osechi, while it comes boxed, is not intended to be eaten at the restaurant in one sitting or at home in one sitting either. It is basically take-home food that a family would enjoy nibbling from for the first two or three days of the new year. So people (if they donft prepare at home) make a pick from catalogues and book ahead.
I usually reserve mine at a department store in late Dec. and go pick it up on the 31st. Once reserved one at a convenience store and had it delivered.
You can probably buy the different food separately at a supermarket and seem blue your own as well.

The last gseem blueh was supposed to behassembleh! Sorry for the typo.

Thank you very much!

Indeed, often see osechi as a hearty meal in stack of boxes to be enjoyed by a group/family. I'm not sure if Osechi is referring to the special arrangement of the food or if has specific ingredients marking the New Year that can be packed for individual serving :) (that would be a bento, I guess!)

Sorry, a side track question, will the department store basement (which sells food) typically open on the 2nd day onwards?

For convenient of housewife and others, nowadays most supermarket have pre-pack/made osechi dishes where you can pick n mix to your liking, arrange it yourself. Or you can pre-book the osechi set online or at supermarket.

You can easily google for osechi dishes and it meaning/represent.
Here's what wikipedia have to say about Osechi Ryori
https://en.wikipedia.org/wiki/Osechi

"Osechi" is basically traditional New Year party dishes. It's a word similar to "Christmas dinner". It doesn't have to come in a box. It's just that a lot of people prefer to tuck them in boxes called "juubako" so that it's easier to handle them at the party.

Since stores don't close on New Years nowadays, it's possible to walk into a store such as a supermarket on New Year's Day and buy ready-made pre-packed dishes. For example, you can buy a pack of ready-made beans, another pack of ready-made egg loaf, and so on. Then you can go to your hotel room, cut the packs using a pair or scissors, and place them on a dish to eat.

Note that osechi is designed to be enjoyed with zouni which is a soup containing mochi. If you eat only osechi, you will be getting too much salt.

Unlike Christmas dinners, osechi is not typically served at restaurants. Even if you stay at a quality hotel on New Year's Day, you only get a limited variety of osechi dishes on your breakfast buffet.

As suggested, if you want something relatively authentic, you have to book ahead as a party. A better way is to find a Japanese friend who would invite you to his/her home during Jan 1-3.