World — Trigger Episode 4

: During a flashback, Osamu is shown filling out a bubble-in aptitude exam for Border with his left hand. This exam was critical because Osamu originally failed to enter Border through normal means and had to rely on other methods (implied to be related to Yūichi Jin's influence) to join.

: At school, bullies are seen throwing paper balls at Yūma's head during class, attempting to provoke him before they are eventually humiliated. Episode 4 Summary

: While broadly discussed in the series, Yūma Kuga has referred to human money as "just paper". This highlights his perspective as a Neighbor who finds human currency and social structures confusing or trivial.

: The episode centers on Ai Kitora demanding that Osamu be punished for his unauthorized use of a Trigger based on strict Border rules. This "on paper" regulation is a major plot point, as Kitora values the hierarchy and official protocols of the organization.