Prologue: Nii-san?

[Rewrite in the works!]

Naoto Shirogane was an ace detective. When she was young, she had a cousin named Makoto Yuki, whom she dubbed as her Nii-san for being close to him.

Naoto always received letters from Makoto...but when they stopped coming after a year...she feared for the worst.

What happened to Makoto? Where is he?

Only time will tell.

And perhaps, he returns.