The two Japanese syllabaries with their romanization.
These marks are not syllables: they change how the kana beside them are read.
っ ッ
A つ written small is not pronounced: it doubles the following consonant and marks a short pause, like the difference between "kite" and "kitte". It never appears at the end of a word.
ー
It holds the preceding vowel for one extra beat. It is used only in katakana, mostly in loanwords, and is written horizontally even in vertical text.
おう えい
Hiragana does not use ー: a vowel is lengthened by adding another vowel. お is almost always lengthened with う (and sometimes with お), and え with い.