Seat 4B's Ghost

After her twin sister's death, Yoon-seo transfers to a new high school and is assigned the exact desk her sister once used. The boy sitting beside her, Do-hyun, reacts as though a ghost has taken that seat. What begins as a cruel coincidence unravels into a trail of unsent letters, borrowed habits, and one sealed message hinting that Yoon-ah understood far more than anyone wanted her to.