Do you write W in Japanese?

The letter 'w' by itself cannot be written in Japanese. The Japanese writing systems of Hiragana and Katakana require both a consonant and a vowel to constitute a single character. Therefore, even though there's no 'w' in Japanese, there is a 'wa' and 'wo'.

Hiragana:

Wa - わ

Wo - ã‚’

Katakana:

Wa - ワ

Wo - ヲ