Kizumonogatari I: Tekketsu-hen (Kizumonogatari I: Blood and Iron Arc)
"I think it's about time I talked about Kiss-Shot-Acerola-Orion Heart-Under-Blade. I believe it's something I have to do. I met her in the spring break between my second and third years of high school. That meeting had such impact and was also quite devastating."
[Source: Araragi Koyomi novel synopsis]