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Why is a title like this so hard to find? The visual novel industry, particularly during the 2000s and early 2010s, produced thousands of "doujin" (independent) titles. Many of these games were released at Comiket (Comic Market) in limited physical runs on CD-ROMs. Once the event ended and the stock ran out, the game essentially ceased to exist in the commercial market.
A concrete next step (if one sought verification)
: Typically, stories with such titles might revolve around themes of love, growth, and perhaps the transient nature of life or relationships, much like the metaphor of a sunflower (which often symbolizes loyalty, devotion, and longevity) blooming in the evening (which could signify a short-lived or rare occurrence).