Katakana

Katakana, the sister script, is identical in sound to hiragana and uses the same five vowels.
Only the shapes are different.

It is the script Japanese uses for words borrowed from other languages and for the sounds of things.

When you travel, katakana is the script that most often rewards you, because once you can sound it out, you discover that many of the words are borrowed English hiding under Japanese pronunciation.

The word "hotel" is written in katakana,
"taxi" is written in katakana,
"ramen" (which is really Chinese noodles) on a shop sign is often written in katakana,
"Terebi" is television,
"Kōhī" is coffee,
"Toire" is toilet.

Because the sounds are identical to hiragana, the five vowels carry over without change.

Where hiragana is round and flowing, katakana is angular and sharp, built from short straight strokes.

Here is the full set of katakana, laid out exactly as the hiragana chart, so you can see that only the shapes have changed.

	a	i	u	e	o
—	ア a	イ i	ウ u	エ e	オ o
k	カ ka	キ ki	ク ku	ケ ke	コ ko
s	サ sa	シ shi	ス su	セ se	ソ so
t	タ ta	チ chi	ツ tsu	テ te	ト to
n	ナ na	ニ ni	ヌ nu	ネ ne	ノ no
h	ハ ha	ヒ hi	フ fu	ヘ he	ホ ho
m	マ ma	ミ mi	ム mu	メ me	モ mo
y	ヤ ya		ユ yu		ヨ yo
r	ラ ra	リ ri	ル ru	レ re	ロ ro
w	ワ wa				ヲ wo
n	ン n

The same two marks appear here as well.
The dakuten strokes soften a consonant, so カ ka becomes ガ ga.
The handaku circle turns the h row into a p, so ハ ha becomes パ pa.

A long vowel is not written by repeating the vowel but by a single horizontal bar, called chōonpu.
So the long oo in a borrowed word is a bar, and rāmen appears as ラーメン, with the bar holding the a long.
When you see that bar, simply hold the vowel before it.

Between the two kana charts you now have every basic sound in the language, and every one of them rests on the same five pure vowels.