words

Not quite.

sushi

You said Old Norse. It's Later and wider borrowings.

How that family writes these sounds

no consonant clusters, every syllable open Japanese: write it exactly as it soundstsunami, sushi, karaoke, futon

What gives it away on the page

no consonant clusters, every syllable open Japanese.tsunami, sushi, karaoke, futon, tycoon

Another word → · the full story of sushi · Later and wider borrowings in the guide