A couple huddle together under one windbreaker on a ferry's top deck, heading back from Shikoku. The speaker's mind drifts to an ex-governor who crossed the same waters a thousand years earlier. The poem seems to allude to the idea of a man imagining a woman as the author of a travel log, filled with songs and poems. I can't say for certain which historical figure Bonta has in mind, so it's safest to read this as the speaker's own reflection on that old voyage.
The ending turns the poem toward the speaker himself. The woman beside him has a name that means safety or refuge, and the speaker guesses she may be thinking he is harder to deal with than she expected. The mood is intimate but gently wry. There is warmth in the shared jacket, yet also self-mockery: while she is right there with him, he is lost in the past, and the poem suggests that this distance is exactly what she is noticing.