N3 — outside your level filter
never + write + not
kesshite kakanai
never; by no means — a flat denial the speaker stakes a judgement or a promise on
meaning: never write
一度した約束は、決して破らない。
ichido shita yakusoku wa, kesshite yaburanai.
A promise once made is one I never break. neutral
このことは決して誰にも言わないでね。
kono koto wa kesshite dare ni mo iwanaide ne.
Don't ever tell anyone about this, OK? casual