Cereal, oats and other foods

Hi,
I will be in Japan for 2 months at the end of the year. To help out my purse and also to help with missing home flavours I was thinking about taking a little food with me.
Can you tell me if the following can be taken in to Japan?

Breakfast cereal
Granola
Porridge oats
Powdered Heinz Soups
Marmite
Chocolate
Peanut butter
Jam
Cheese

If allowed, does any of this need to be declared on the form when entering the country?

Thanks for your help

Don't know about customs laws, but out of your list the following can be easily found in any supermarket Japan:

Breakfast cereal, although the selection is limited compared to the US or Europe.
Chocolate
Peanut butter
Jam
Cheese, although expensive

Nothing of the things you listed should be difficult to bring to Japan, as long as you don't bring huge amounts. Except the cheese everything else is also easily to be found in Japan, at least unless you go to remote areas. So you might consider bringing more personal items rather than food.
Cheese can be found in Japan, however is expensive (to very expensive for the really good stuff). So bringing some excellent cheese might be worthwhile.

Don't bring meat products though. They are not allowed and if found will be taken away. Same goes for fresh fruits.
Enjoy your life in Japan!

Thanks ever so much for the replies.
If I'm about to buy in Japan, ill avoid taking.
How are English tea bags to come by?
I know Japan has tea everwhere, but I tend to get headaches if I don't have a proper cup of tea for a few days!!!! (yes, I know that's bad!)

Tea bags (if that's your definition of "proper cup of tea") can be found. E.g. at stores like Kaldi but most likely also at normal super markets. (I don't really go shopping at supermarkets but mostly Kaldi for overseas products and home delivery for standard food).

Here the web page of Lipton (in Japanese, but just as proof that it exists in Japan): http://www.lipton.jp/

If you have free space in your luggage, totally bring some tea, cereals or what you like (after you have filled them with all the cheese you want to eat). But don't worry, all these items are easily to be found.

Thanks for your help

If you will be living in a rural area you may have to travel a bit to go to an "import" shop, but a lot of larger English tea brands (Twining's, etc.) are available in quite a few places here. You can even get clotted cream at Seijo Ishii. Granted most of the items you listed will probably be a bit more expensive than you're used to, but you can get quite a lot of international food items these days if you really want them and are willing to pay a bit.

I often eat granola（グラノーラ） or oatmeal（オートミール） for breakfast recently.
I often eat Calbee's frugra（フルグラ）, but other types are also sold to supermarkets.
Oatmeal is bought only at Amazon.co.jp now.
Amazon.co.jp is also available in English.
However, although there may be few kinds, we also sell it at imported foodstuff stores such as supermarkets and Kaldi. (Perhaps Seijo Ishii, Kinokuniya, National Azabu etc. → These are luxury supermarkets)