This should probably be written in the Katakana section; however, when writing vertically in Japanese, make sure not to mix up 一(いち)and ー (extended vowel). Many foreigners tend to mess this up. When writing vertically in Japanese 一(いち)remans horizontal, while ー (extended vowel) is turned 90 degrees to become vertical.
So if you write 11, it would be:
十
一
If you write cake, it would be:
ケ
l
キ
Please remember this if you write vertically. Other wise it will confuse people.
A friend of mine went to Madrid, Spain and bought a Japanese shirt (why it was in Japanese, I don't know), anyways, the shirt has the cities name written on it vertically in Japanese and instead of saying マドリード(Madrid) it said マドリー(いち)ド. (._.) Do not make that mistake please.