Gosho Aoyama's Collection of Short Stories

A genius inventor, who is still a high school student, has a girlfriend two years older than him. One day, he invents a time machine and attempts to go two years back into the past, to become the same age as her. However, it is she who ultimately uses the machine to travel through time!

A handsome detective, Kudou Yuusaku, receives phone calls from a mysterious woman day after day, with a new case each day. He of course solves them one by one. But the biggest mystery is who is this mysterious woman?