According to Media Factory, Matsuno Akinari, the author of MM!, passed away on April 18th. He was 32 years old. MM! novel will be left incomplete. His last tweet was posted on September 9th. He was talking with Endou Minari and Hyoju Issei about MM! anime.

Matsuno's last tweet

Endo Minari said she attended his funeral last week and knew he was the same age as her. She was so sad that she has been at a loss what to do. Hirasaka Yomi said he could not face his friend's death.

Sources: Media Factory, Endo's twitter