A work done by U. MAIA (the M, A, and I standing for Mizuno, Akatsuka and Ishi(no)mori respectively). An early work done while the three were at Tokiwa-so together.
(from ebookjapan):
Hideko Mizuno, Fujio Akatsuka, and Shotaro Ishimori worked together on the mystery "The Angel of Darkness". The day before a murder over a diamond that brings misfortune, "The Eye of the Shinigami", Chiko-chan happens to witness the victim, Yamagata, arguing with each other. ...... With her police officer father and newspaper reporter brother by her side, Chiko gets to the bottom of it! Also included is "And Miya is Gone," a story done with Fujio Akatsuka.