Sherwin had often found himself looking out of his classroom's big transparent partition, towards the class that could be seen on the other side of the corridor. The focus of his vision was no one other than the class leader of the other class, Joshua, who he wants to draw a portrait of.
Sherwin's crush on Joshua was meant to end as an unrequited love.
However, things drastically changes when Joshua suddenly finds himself staring at a fanart of himself, displayed on the school's bulletin board and gets hell-bent on finding the artist of the piece of art.
A love letter written long ago for a 'certain someone' is accidentally found by that certain someone coincidentally.
With little to no clues about the writer, Ssiva, the 'certain someone' decides to find the writer.
°°°
Elaborated description is added in the prologue episode.