I’ve looked into this a bit because the question comes up a lot. 'Poem of Secret Love' is a modern romance novel, and from everything I can find, it's not based on a specific, documented true story in the way a biographical novel would be. The author hasn't made any public statements claiming it's autobiographical or directly inspired by a single real-life event.
That said, the feelings it explores feel incredibly genuine. The pining, the missed connections, the quiet sacrifices—these aren't fantastical inventions. They're drawn from the universal human experience of unrequited or hidden love. So in a sense, it's 'true' in the way that all good romance feels true: it mirrors emotional realities many of us have lived, even if the specific characters and plot are fabricated.
What makes it feel so real, to me, is the detail in the mundane moments. The way the protagonist remembers the exact shade of the sky during a particular glance, or the specific weight of a gift they never gave. Those tiny, hyper-specific observations are what give fiction the texture of memory, and that's probably where the 'based on a true story' rumors get their traction. It resonates because it captures truths, not because it documents one.