Real idiom for total, undivided focus.

What a Japanese person actually thinks
Disciplined and slightly old-fashioned — the register of a craftsman or a martial arts hall. Reads as someone who takes something very seriously.

Meaning

Literally: one intent + exclusive heart
Actually: Devoting yourself to one thing with your whole mind.

Scores

Naturalness●●●●●

Established yojijukugo.

Coolness●●●●●

Strong and specific. Slightly stern, which is either the point or isn't.

Watch out

Nothing embarrassing lurking in here.

On skin

一意専心

Orientation: vertical

Mincho, vertical column.