Real word, genuine history — and serious wartime political baggage.

What a Japanese person actually thinks
Depends entirely on who's reading. Some see a classical literary term. Others see a right-wing slogan — the sort of thing on a sound truck. A foreigner wearing it reads as either badly informed or making a statement.

Meaning

Literally: Yamato (ancient Japan) + soul
Actually: 'The Japanese spirit.' Originally a literary term, but heavily used in WWII-era nationalist propaganda and still associated with it.

Scores

Naturalness●●●●●

The Japanese is correct and the word is real.

Coolness●●●●●

The politics swamp the aesthetics.

Watch out

highStrong association with imperial-era nationalism. In Korea, China, and among many Japanese people, this reads as a political statement, not a cultural one.
mediumIt specifically means the spirit *of the Japanese people*. Worn by a non-Japanese person it doesn't parse as 'I am spirited' — it parses as a claim about nationality.

Get this instead

武士道 bushidō
the warrior's code

The martial-spirit meaning without the nationalist reading.
不撓不屈 futō fukutsu
indomitable

If you wanted 'unbreakable spirit', this says it with no political charge at all.

On skin

大和魂

Orientation: either

N/A — reconsider the words before the typeface.