Most of the teaching jobs I see advertised in the Saitama area are ALT positions, meaning "assistant language teacher". Junior high/high schools often hire ALTs to assist regular Japanese language teachers. The regular teachers are knowledgeable in grammar and such, and the ALTs teach the students pronunciation and real-world use.
The English you used in your post was not up to par. Most places in Japan who hire foreign teachers with no experience are going to want a demonstration of your English ability. At the very least, you will be interviewed on the telephone by someone who will be listening carefully to your English, and how well you use it. At most, you will be required to write an essay as well as submit to a telephone interview.
Without looking it up, can you give a samples of sentences in the passive and active voice? Can you give examples of 1st, 2nd, and 3rd conditional sentences? Can you give examples of sentences in various tenses, from past simple to future perfect continuous? How about gerunds and infinitives? What are they? How about phrasal verbs? Separable? Inseparable? Can you give examples of each?
At the places I applied, I was asked the above questions, or was required to complete a test which included them.
Getting a job teaching young children exclusively does not mean you don't need good English. Most childrens schools are run by companies who require prospective teachers to pass a basic English test. Japanese teachers who teach children will usually have to have obtained a decent score on the TOEIC test.
Even if your English is better than that which is shown in your post, you had better start studying now. Better yet, take a TEFL course, it'll be time and money well-invested.
If you do come to Japan, and do need to buy materials, you can find them (and other things you might need) here:
FBC, The Foreign Buyers' Club