Board Thread:General Discussion/@comment-26429365-20170422094921/@comment-217.212.214.57-20170422095411

Simple. Pure logic and deduct

Yoriko's friend is the waitress = The waitress works at Re = Haise often went to Re = Haise liked the waitress = Haise is at Re.

Simple deduction. Mutsuki is an investigator after all.

That he was actually there at the time was just sheer luck though...