Fault!!

A high school guy named Shuichi spends his days playing tennis with a small five-person club, enjoying the easy rhythm of school life. Then an accident sidelines him with an injury, and suddenly his world gets a lot more complicated. Ai, one of his club members, steps in to take care of him, attentive, warm, clearly invested in his recovery. Meanwhile, his younger sister Mio is anything but warm about the whole situation, staying persistently grumpy in a way that creates this low-key tension running through everything. Then something bigger happens that shifts all of it. The relationships between these three are the real engine here: it's a character-driven setup where the dynamics feel lived-in before things start unraveling. Based on a visual novel, the 3-episode OVA from T-Rex does lean into that source material's strength: spending time with characters before pulling the rug. If you've watched something like Stringendo or Resort Boin and appreciated when a short-form hentai actually bothers to establish who people are before jumping into content, Fault!! is in that lane. It's not trying to do anything groundbreaking, but it's more grounded than most entries in the genre. The tennis club setting keeps things feeling specific rather than generic, and the sister dynamic adds a friction that makes the character interactions feel like they have actual stakes. Short commitment, relatively coherent story for what it is.