Kou is Umiko's co-worker who always calls her by her surname which always results from her shooting the former. They are close enough to engage in a drinking contest and a duel.
Rin is Umiko's superior. There isn't much interaction between the two but they're close enough for Rin to call her Umiko-chan.
Shizuku is Umiko's superior who annoys her to extent that she shoots Shizuku when the latter nonchalantly changes the game's specs, not caring that the Shizuku is the Director. Umiko often searches for Shizuku when she needs something and the latter is not in her office.
Umiko takes interest on Aoba to the point that she always invites and converses with the latter about playing Airsoft. She thinks of Aoba as much more responsible than Nene.
Nene is Umiko's subordinate when the former is beta testing for Fairies Story 3. She recognizes and praises Nene's talent on beta testing. After Nene's part time beta testing is finish, she and Umiko still talk and meet up with each other. Umiko mentors Nene on programming when the latter takes interest in it.
Umiko starts interacting more with Hifumi when the latter replaces Kou as the Character Team Leader. Hifumi is wary of Umiko and feels like the latter is hard to talk to, to the point that Hifumi frightfully asks Kou if she needs to talk to Umiko in meetings.