Koji Seno (瀬野 浩二 Seno Kōji) is the younger brother of Takami Seno who used to be a regular at Moffle's House of Sweets until they changed it.
Koji is a hardcore gamer that enjoys challenging and difficult games. That's one of the reasons why he liked Moffle's House of Sweets so much. Moffle noted that Koji may be a bit different from other children, as kids his age were more apt to mock amusement park attractions then praise them.
He may have a case of superiority, as he refers to those who simply play the game for fun as "casuals" and "plebs". He admired Moffle, and made him promise not to turn it into a "boring pleb ride". But when Moffle changes the House of Sweets, he acts betrayed and accuses Moffle of being drunk on his fame and forgetting the regulars.
Koji is also protective of Takami Seno, which is shown when Moffle (disguised with a Lalapatch Charm) brings home Takami while she's drunk. When he sees Moffle, he walks away from him and goes back to his room.
Koji is currently in middle school, but he does not go to school. Instead, he spends most of his time at Amagi Brilliant Park, playing at Moffle's House of Sweets.
Koji cares for Takami. He was upset when saw Moffle(disguised with a Lalapatch Charm) bring Takami back to their house drunk. He also told Takami that the job of Civil Service suited her.
Amagi Brilliant Park
Koji used to love Moffle and went to his House of Sweets all the time, even when the park wasn't doing well. He especially liked his attention to realism in his games, and how they captured "the true soul of the battlefield". However, when Moffle was forced to cut his wait times to prevent the lines from coming to long, he felt betrayed and accused him of forgetting about those that had stuck with him the whole time, then left, swearing to never comeback.
- The name Koji means "prosperous" (浩) (ko) and "two" (二) (ji).
- Koji's surname Seno means "swift current, rapids" (瀬) (se) and "field, wilderness" (野) (no).