必 means “certain, without fail”

かならず · kanarazu

Also: invariably, inevitable

Kun'yomi (Japanese reading)
かならず
On'yomi (Chinese reading)
ヒツ

JLPT N3 · Taught in grade 4 · 5 strokes

The story

Picture a heart pierced straight through by a spear: once something is pinned that firmly, it is bound to happen. 必ず means "without fail", 必要 is what you cannot do without, and 必死, "certain death", is giving it everything.

Used in 必ず (kanarazu, without fail), 必要 (hitsuyou, necessary), and 必死 (hisshi, desperate/all-out)

More from Cause & Reason

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Readings from KANJIDIC2, © EDRDG, CC BY-SA.