Imasara ni kimi wa iyukaji harusame no kokoro o hito no shirazu aranaku ni

今さらに君はい行かじ春雨の
心を人の知らずあらなくに

Roma-ji: Imasara ni kimi wa iyukaji harusame no kokoro o hito no shirazu aranaku ni
English Translation: Now, at this late time,
you will surely not set out;
for the rain of spring—
its heart is not a thing
unknown to anyone at all.
Meaning: Surely you will not go out now, at this late hour. It is not as though one could fail to know the heart of the spring rain, which falls to keep you here.
Commentary: Book Ten Spring Love Poems 1916

Headnote continued from the preceding poem: "Love Expressed Through Rain"
This poem treats the spring rain that has begun to fall as the rain's own wish to hold back the beloved, saying surely he will not go out now. Attributing will to the rain and letting it speak for the speaker's wish to detain him, it is a witty expression. Whereas the preceding poem came to the beloved regardless of the spring rain, this one uses the rain as a pretext to keep the beloved from leaving, so the one who comes and the one who detains form a pair.

The first line, "imasara ni," means now at this point.
In the second line, "kimi wa iyukaji," "i" is a prefix and "ji" a negative conjecture: you will not go. The poem breaks here.
The third line, "of the spring rain," qualifies "heart," personifying the rain.
The fourth line, "its heart, people," takes "hito" to mean either the lover or people at large.
In the last line, "shirazu aranaku ni," "naku ni" is a nominalized negative with "ni," meaning it is not as if they did not know. By inversion it gives the reason at the end.
Source: Manyoshu
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