Real word, two dense characters, and it actually means fighting spirit.

What a Japanese person actually thinks
Hot-blooded in a way Japanese people find endearing rather than embarrassing. Sports register — a banner in a stadium, a headband. Sincere and a bit shouty, in a good way.

Meaning

Literally: fight + soul
Actually: Fighting spirit — the refusal to be beaten. Famously the motto of wrestler Antonio Inoki, so it's firmly in the national vocabulary.

Scores

Naturalness●●●●●

A real, current word.

Coolness●●●●●

Genuinely strong. The Inoki association is a plus if you like wrestling and neutral if you don't.

Watch out

lowThe sports/wrestling association is strong enough that some readers will assume you're a fan. That's a pretty benign assumption.

On skin

闘魂

Orientation: vertical

Bold brush. This word wants to be shouted, and the typeface should agree.