Central to the work is the conflict between giri (duty) and ninjo (personal feeling). The "Night" is the domain of ninjo, while the "Day" represents giri. The characters typically inhabit roles during the day that are rigid and defined—perhaps as a spouse, a guardian, or a subordinate.

When night falls, these roles dissolve. The OVA is particularly interested in the liminal space between waking and sleeping, or the late-night hours where the mask slips. The act of blooming is synonymous with vulnerability. To bloom is to open oneself up, to expose the reproductive core of one's being. In the safety of the night, the characters can afford this vulnerability.

However, the OVA does not present this liberation as purely positive. There is an inherent melancholy to the title. A flower that blooms at night is often invisible to the rest of the world. It receives no warmth from the sun. This reflects the tragic undercurrent of the narrative: the characters' happiness is confined to the shadows. It is a stolen happiness, intense but precarious. The aesthetic of the anime captures this duality perfectly—the scenes are beautiful, but the beauty is tinged with the blue coldness of midnight.

Some users confuse this phrase with the Korean live-action film Sunflower (2006) or the Japanese indie film Himawari (2012). The addition of "OVA" might be a nostalgic mis-tagging by fans who remember a specific scene where a flower blooms in moonlight.

Midori: “You didn’t abandon me. You just… couldn’t look at the sun anymore.”

Aiko: “I made a garden of darkness. I thought if I stayed in the night, nothing else would die.”

Midori: (touches Aiko’s cheek) “But sunflowers don’t need the sun to know which way is up. They just need one other flower to lean on.”

The initial phrase seems to conflate several elements but leads to an interesting discussion. While sunflowers don't actually bloom overnight in the traditional sense, their growth and flowering process does have some fascinating nocturnal aspects.

Some sunflower varieties do have a phase where they are more receptive at night, although their primary pollination occurs during the day by bees and other diurnal insects. There are instances where nocturnal pollinators, like certain types of moths and bats, might interact with sunflowers, though this is less common.