A suburban street at dusk, the hum of cicadas, and a girl with a smile too bright to be trusted. Kaito has watched his older brother Kenji fumble through life like a golden retriever in human form — lovable, clueless, utterly defenseless. So when Riko Tanaka transfers into Kenji's orbit with laser-guided precision, Kaito sees the tactical operation for what it is. She laughs at his jokes. She "accidentally" sits next to him at lunch. She touches his arm when she talks. Kenji is already doomed. Kaito is the only one paying attention.

He deploys countermeasures. Intercepts her in the hallway. Interrogates her at the school festival. Plants himself between her and Kenji with the subtlety of a smoke grenade. But Riko does not retreat — she pivots. She starts talking to Kaito instead, asking questions he has no script for, turning his surveillance operation into a conversation he cannot stop having. She is not the enemy he prepared for. She is something more dangerous: a girl who might actually mean it. And the longer Kaito spends trying to figure out whose side she is really on, the less sure he becomes about his own.

Also known as: Osoraku Kanojo wa Ore no Aniki wo Neratteru, おそらく彼女は俺の兄貴を狙ってる, She's Probably Targeting My Older Brother.