A manga that turns childlike drawings into cryptic puzzles, Strange Pictures follows an interconnected web of amateur sleuths trying to decode disturbing messages hidden in innocent sketches. At its core lies a set of nine pictures. A pregnant woman posts numbered doodles on her blog, seemingly imagining her unborn son's future, but the drawings conceal a dire warning addressed to her husband. A young boy named Yuta creates a simple crayon drawing of his home for a nursery school project, yet the image holds a message that no child should know how to express. A murder victim leaves behind a final sketch on a receipt, and three years later, that drawing becomes the only clue for someone trying to solve the crime.

The story unfolds through a shifting cast of characters whose paths initially appear unrelated. Two college students, Sasaki and Kurihara, belong to their university's occult club. Kurihara discovers an enigmatic blog that stopped updating years ago, written by a man named Ren whose wife, Yuki, died in childbirth after leaving behind a series of strange pictures. The husband believed his wife was trying to communicate something crucial through her drawings, and the two students become obsessed with decoding the blog's secret. In another thread, a widow notices the troubling drawing made by her five-year-old son, while a nursery teacher finds herself drawn into the mystery. A young newspaper administrator who aspires to be an investigative journalist takes on a three-year-old cold case, following the lone clue of a sketch drawn right before the victim was murdered.

As these separate investigations progress, each set of drawings reveals hidden messages that can only be seen from specific angles or by understanding coded visual language. The manga includes the childlike sketches themselves along with close-ups of certain details, graphs, and diagrams that invite the reader to solve the puzzles alongside the characters. What emerges is a slow convergence around a young boy and the woman he calls Mama, with the seemingly disconnected cases circling back to shared truths concealed within the images. An art teacher's murderer is identified through a scrawled receipt, a psychologist trained in analysis gets everything wrong while the amateur internet detectives piece together the evidence, and each chapter topples prior assumptions while building toward a resolution that connects every picture. The narrative structure treats the internet itself as both a tool and a trap, showing how online voyeurism and obsessive amateur research can uncover buried crimes, even as the characters stumble through clunky coincidences and overexplanatory theories.