I had totally missed it!!! Keen eyes you have!!
Hair down, I'm guessing this was when he was still a teenager or before he became a boss of the group. Whose the dark haired man next to him....
Yep, it's Yashiro as a younger man with Misumi. Seeing as the author has already shown a crossover, wouldn't it have been quite sweet if Masaki from NightS was the one involved in arresting Ryuuzaki in Saezuru... that probably would have been to obvious, but it would be interesting to see Masaki again and how his calm demeanor would react to the more fiery Ryuuzaki-kumicho.
OH MY WHAT A GREAT SURPRISE! DIDN'T EXPECT TO SEE YASHIRO CAMEO HERE. THANKS SENSEI!
http://www.mangago.zone/read-manga/op_yoake_itaru_no_iro_no_nai_hibi/mi/37aab174953a79e82add09c50a0739d7_chapter-6/12/