Fault!! Service: Aratanaru Rival

Returning from summer break, Shuuichi Sugiyama finds two classmates, Ai and Mio, competing for his attention in ways that make getting through a normal school day genuinely complicated. That alone would be enough to deal with, but then the tennis club president Reiko decides the club needs to run a cosplay café at the school festival, throws her name into the race for student council president, and a mysterious transfer student shows up to shake things up even further. The guy cannot catch a break. This is a one-episode OVA adapted from a visual novel, so the pacing moves quickly and it leans hard into the romantic rivalry setup. The school festival and cosplay angle give it a lighthearted, youthful energy; it is not trying to be serious, and that works in its favor. The character dynamics have enough personality that the setup feels lived-in rather than just a collection of tropes going through the motions. If you have watched something like Stringendo: Angel-tachi no Private Lesson or Resort Boin and liked the school-based romantic setup, this fits comfortably in that space. It is produced by T-Rex and carries that familiar visual novel adaptation style: character-focused, scenario-driven, with clean animation that does the source material justice. One episode, straightforward premise, no buildup required. You know what kind of show this is going in, and it delivers exactly that.