I'm a ronin with a stunning stepsister, and lately I've been troubled by her new hobby. It's a fitness routine similar to aerobics, and her voluptuous figure clad in a leotard, especially the V-zone, has been burned into the depths of my mind. Because of that, I can't focus on studying at all these days. As if aware of my inner turmoil, my stepsister Honami continues her daily workouts, and I find myself obsessively tracking the changes in her body and mind.