He is the forgotten person Lu Jinyan who has been trapped in the "Ember Space" for hundreds of years. No one can see him, remember him, and can't even touch him. He will completely disappear at any time.
He is Su Nian, an ancient book restorer, who is born with the power of memory - he can awaken the past of forgotten people at the cost of losing his own memory.
The first time he touched Lu Jinyan's old architectural drawings, Su Nian forgot how to mix the paste; the second time he helped him piece together his obsession from a hundred years ago, he forgot the agreement he made with his best friend; the third time, he almost blurred his own name, but still stared into Lu Jinyan's eyes and said, "I remember you, Lu Jinyan."
Lu Jinyan pushed him away with red eyes: "Forget me, you can live." But Su Nian insisted on fighting against this "curse of forgetfulness" - exchanging his own memory for his existence, and using the bond between the two to ignite the dying embers.
When the truth was revealed: Lu Jinyan was an old friend of his ancestors, and Su Nian's power of memory was born to protect him. In the end, they broke the fate of being abandoned by time, and let "the embers never burn out, stay together day and night" from a promise to a warmth passed down from generation to generation.
Concept: Love and obsession are the ultimate forces against forgetfulness. Two-way protection and redemption can keep the warmth buried by time alive, allowing bonds to transcend life and death, and coexist day and night.