An artist painted two angels for his mural in an art shop. At night, the two angels magically turned to life. Julius, one of the angels, accidentally meets the artist. The two became friends and Julius somehow modelled for his artist. Upon realizing the truth, their separation has come. Now, it's Julius' decision to follow his artist with the risk of disappearing or staying with a look of regret, ultimately ruining the mural. Turns out, mutual love makes them human.
10 years after, the angel Marion meets his own destined human. A brokenhearted novelist fell unconscious under him and their meeting became alphabetic lessons, ultimately making Marion love to write letters. Just when Marion realized that he could be human, he feared that the novelist is too in love with his ex-lover to love him back. So, he wrote letters to the novelist without meeting up with him. However, the new caretaker of the art shop is planning to paint over Marion and the novelist just realized who the angel was. Anyway, in a desperate attempt to stop his friend from painting over the mural, the novelist hurt himself and Marion who lost one of his wings sought for him. By dawn, they meet and Marion has become warm to touch.
The novelist and Marion painted over the wall as compensation for the chaos the ensued prior. And that's when the Artist and the grown up Julius reunited with Marion. Turns out, they age once they turn human.
Kabe no Naka no Tenshi