Revealing spoilers is never a good idea, especially if it concerns someone's favorite anime. This is particularly true if the person happens to be a member of the kendo club and carries a katana.
Unfortunately, Terada made the blunder of disclosing a spoiler that pertained to Hikami's cherished anime. As a result, Hikami sets out on a quest for retribution and soon, a war of spoilers ensues. The situation spirals out of control, culminating in complete chaos.