A long, black fabric strap lay nestled inside the package. A hardened component was integrated into the center, flanked by strips of what looked like rubberized plastic.ย
Yuzuki glanced to the side. A device the size of a smartphone sat next to it.
"A heart rate strap... I can't believe Agnes Tachyon actually developed something like this. The girl really is a genius."
The strap worked by using two large rubber electrodes to measure the electrical activity of the heart. It was far more precise than any commercial wearable watch.
Yuzuki picked up the remote. The top featured a small display screen, flickering with various numerical values related to cardiac rhythm.ย
Below the screen sat a row of buttons. He leaned in, squinting at the tiny labels etched beside them.
[๐๐ป๐ฐ๐ฟ๐ฒ๐ฎ๐๐ฒ ๐๐๐ฟ๐ฟ๐ฒ๐ป๐]
[๐๐ป๐ท๐ฒ๐ฐ๐ ๐ ๐ฒ๐ฑ๐ถ๐ฐ๐ฎ๐๐ถ๐ผ๐ป]
"Whoa, whoa... what kind of functions are these?"ย
His instincts screamed at him to leave those buttons alone. For the sake of Fujimasa March's safety, he wouldn't even breathe on them.
"I'll have to be careful with this thing. God only knows what that Uma Musume's original intention was. I wouldn't be surprised if she added some lethal features just for the hell of it," Yuzuki muttered, sighing.
Still, his eyes brightened as he gripped the device.ย
"With this, the training plan can finally get on track."
In his previous life, every running enthusiast and professional athlete relied on heart rate data. It wasn't just a health metric... it was the ultimate tool for controlling training intensity.
The body reacts to stress in predictable ways. The heart beats faster.ย
By monitoring those shifts, a coach could determine exactly how much pressure the body could handle.ย
If the intensity is too low, the body isn't stressed enough to improve. If it's too high, the body breaks.ย
Scientific training was built on the foundation of heart rate zones. Each zone yielded a different physiological result.
E, M, T, I, and R.ย
These five letters formed the backbone of any elite program.ย
E stood for Easy Run. M was the Pace Run. T represented Threshold Run. I was for Interval Training, and R stood for Repetition Training.
Each had a specific purpose.ย
The Pace Run mastered rhythm. The Threshold Run built lactic acid tolerance. Interval Training boosted maximum oxygen intake, while Repetition Training forged anaerobic power and top-end speed.
In Yuzuki's plan, Easy Runs made up the bulk of the work. They would happen almost every day, keeping Fujimasa March between 65% and 78% of her maximum heart rate to build her aerobic base.
High-intensity work was reserved for "Quality Days."
The entire distribution was an inverted pyramid. The higher the intensity, the lower the volume. Repetition Training sat at the very peak, the sharpest and most taxing tool in his shed.
This scientific allocation of intensity was Yuzuki's greatest "cheat code" in this world.
He looked out toward the track where Fujimasa March was still pushing herself.ย
"That's enough, March! We're done for today. Go back and rest!"
Fujimasa March slowed to a halt, wiping sweat from her brow. "Already, Trainer? I still have plenty of energy left!"
Thanks to her improved form and breathing, she wasn't even winded.
"No need. Get some sleep. We meet at eight o'clock tomorrow morning."ย
Yuzuki gave her a thin, mysterious smile.ย
Fujimasa March had no idea. The real training hadn't even started yet.
***
The next morning, Yuzuki was still working through his breakfast when his phone buzzed. It was a message from Fujimasa March.
[๐ง๐ฟ๐ฎ๐ถ๐ป๐ฒ๐ฟ! ๐'๐บ ๐ฎ๐น๐ฟ๐ฒ๐ฎ๐ฑ๐ ๐ต๐ฒ๐ฟ๐ฒ. ๐'๐บ ๐ด๐ผ๐ถ๐ป๐ด ๐๐ผ ๐๐๐ฎ๐ฟ๐ ๐บ๐ ๐บ๐ผ๐ฟ๐ป๐ถ๐ป๐ด ๐๐ผ๐ฟ๐ธ๐ผ๐๐ ๐ป๐ผ๐.]
Yuzuki checked the time on his screen.
6:25 AM.
'Can we please not be this competitive?' he thought, rubbing his temples.
He sighed, drained his coffee in one gulp, and typed a quick reply.
[๐ช๐ฎ๐ถ๐ ๐ณ๐ผ๐ฟ ๐บ๐ฒ. ๐'๐บ ๐ผ๐ป ๐บ๐ ๐๐ฎ๐.]
He grabbed a rice ball from the table and bolted out of the dormitory.
By the time he reached the Kasamatsu training grounds, Fujimasa March was already in a corner of the track, her white tracksuit stark against the morning mist.
"Morning, March," Yuzuki called out as she went through her stretches.
She stopped mid-motion and turned, her face bright. "Good morning, Trainer!"
"I thought we agreed on eight o'clock. Why so early?"
"Oguri Cap is already fighting in Central..." Fujimasa March's eyes burned with a fierce, restless light. "How am I supposed to sleep at a time like this?"
Yuzuki felt a surge of satisfaction. Her drive was infectious.
'What a terrifying Aura... just don't go crying when the workout starts,' he thought.
"Keep the stretches slow," Yuzuki added, watching her aggressive movements. "Don't rush it."
"Understood, Trainer." She slowed her pace, focusing on the tension in her muscles.
Yuzuki had taught her this specific routine back when he was still an assistant. It was a sequence he had used constantly in his previous life, and the results were undeniable.
Stretching was non-negotiable.
Pre-run stretches increased joint mobility and muscle flexibility, priming the body for the load and slashing the risk of injury. Post-run stretches accelerated recovery.
But if the form was sloppy, it did more harm than good. Yuzuki watched her like a hawk.
Once he was satisfied with her warm-up, he stepped forward.
"Warm-up is over. March, we're starting the real work now."
He held out the black strap. "We're doing a ten-kilometer slow run. Put this Heart Rate Monitor on."
"Trainer, what is this?" She poked at the black band curiously.
"A secret weapon to make you faster. Now, get to it."
Fujimasa March didn't hesitate. She strapped the device on and began her laps.
As she circled the track, Yuzuki raised the monitor, his eyes fixed on the data stream.
[๐๐ฒ๐ฎ๐ฟ๐ ๐ฅ๐ฎ๐๐ฒ: ๐ญ๐ฐ๐ฑ ๐๐ฃ๐ ]
[๐๐ฒ๐ฎ๐ฟ๐ ๐ฅ๐ฎ๐๐ฒ: ๐ญ๐ฑ๐ด ๐๐ฃ๐ ]
The numbers climbed rapidly, quickly threatening to blow past the Easy Run zone. Yuzuki's brow furrowed.
"Slow down, March!"
The Grind
"Do you really plan on finishing ten kilometers at that pace?"
"Adjust your breathing! Fix your posture!"
"Pick up the cadence! Faster!"
Yuzuki stood on the sidelines, his voice cutting through the air like a whip. He didn't hold back, pushing his lungs until his throat felt raw.
"Listen to your body! If the fatigue starts to bite, you change! Shift your rhythm, adjust your form, but do not let up!"
Fujimasa March was gasping, her lungs working like heavy bellows. Every breath was a deep, deliberate pull of oxygen, fighting against the weight in her limbs.
Yuzuki watched her, a small, sharp nod of approval escaping him.
'The last few days weren't a waste of time. The results are finally starting to surface.'
The change was there, written in the way she held her frame against the exhaustion.
'The old March would have been flagging by now. Ten kilometers wouldn't have looked this controlled.'
He watched her feet strike the track, rhythmic and sure.
'If she can maintain this... we can finally move on to the next phase without any issues.'