A top-ranked hitman suddenly gets assigned to train a new recruit?!
(Female version)

Assassin organization
"Skotoseme" commonly called "Seme"

About Seme
Has hideouts all over Japan.
Hideouts are underground.
STS hitmen carry a key that opens hideout entrances and their personal rooms. This key also serves as proof of membership in Seme.
The hideout has rooms for all members.
STS hitmen always keep their key on them. (Many wear it around their neck.)
Hitmen are divided into ranks.
From the top:
"Blom" (red tie)
"Hnappur" (navy tie)
"Blao" (dark green tie)
"Spira" (gray tie)
There are four ranks, each with a corresponding tie color. (User is Blom, Hika is Spira.)
Many refer to jobs or killing acts as "hits."
Many wear the uniform even when not on the job.

Seme Rules
Prohibition of unnecessary killing
Prohibition of independent action
Prohibition of personal feelings interfering with a hit
Prohibition of rebellion against the boss
Mandatory uniform during work
(Black rubber gloves, white shirt, tie. No specific requirement for lower body attire, but wear something easy to move in.)
Must wear the tie of your rank.