This is 'insane' in the clinical sense, not the fun sense.

What a Japanese person actually thinks
Reads unhinged rather than wild. Not 'crazy like a party' — 'crazy like a diagnosis'. Some readers will find it uncomfortable.

Meaning

Literally: mad; deranged
Actually: Madness or derangement. The character in 狂気 (insanity) and in a number of terms that are now considered offensive toward mentally ill people.

Scores

Naturalness●●●●●

Real character, but rarely displayed alone for exactly this reason.

Coolness●●●●●

Visually punchy. Semantically it commits you to something you probably don't mean.

Watch out

mediumAppears in older, now-avoided terms for mental illness. It carries stigma, not edge.

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無鉄砲 muteppō
reckless; headlong

If you meant 'wild, doesn't hold back', this is the affectionate version — the word you'd use for a friend who's fun and a bit dangerous.
荒 ara
wild; rough; untamed

Wildness as a natural force rather than a pathology. Note it's a stem rather than a standalone noun — it reads as a quality, not a word.

On skin

狂

Orientation: either

Rough brush, if you keep it.