The speaker wakes from a lovely dream about someone they care for: the strong arms, the smooth skin, and above all that crooked smile that starts as a twitch and spreads across the face. Just remembering it sets off butterflies in the stomach, and the speaker happily lets them stay. For them, the butterflies are proof that something good exists in a world where so much goes wrong.
The mood shifts near the end. The memory of kissing under cherry blossoms in broad daylight feels so perfect that the speaker starts to wonder if it ever happened. That small parenthetical question leads to a darker thought: maybe this person was a nightmare all along. The closing "After all" leaves that doubt hanging. The scattered, drifting line placement mirrors a mind half awake, unsure what is memory and what is dream. The poem moves from warmth and giddy longing to uneasy suspicion.