A lonely boy stuck in a grey, grey world, longs for company and understanding. A lonely girl stuck in a world of imagination, silently wishing for friends and new ideas for her sketchbook. Both of their lives unexpectedly intertwine as they both fill each others emptiness in their hearts. Will it be a school year to remember, or one they'd rather forget. M's sketchbook revolves around a boy named Koichi Fujimoto, who has a single childhood friend named Miyoko Yamaguchi. They knew each other through their parents when they were five years old. They even went to the same school. But one day, Miyoko got transferred to a school in Kyoto. Koichi was left behind with no one at his side. Eventually things made a turn for the worst. Out of stress, he was sent to the hospital after he started showing signs of schizophrenia. After months of recovery, he was released. When he arrived for the fifth day back, a transfer student joined the class.