A detective at the Shibuya Central Police Station. Kano looks up to Tateno and has based his detective "Dick Diary" based on the various dictums he provides. He's also identified as "The Man with the Cane" from Achi's perspective. An assassin attempting to hunt down Hitomi Osawa soon after she hands off the ransom money. The full truth is that Tateno is a childhood friend of Achi's parents, having been in love with Kotone even long after her death. Daisuke asked Tateno to kill Hitomi so that her heart could be transplanted into Suzune and save her from her terminal heart condition.