Working Out While Getting Teased by Nagatoro-san Is So Productive
Table of Contents
Having bought a smartwatch, I decided I really ought to get active, so I’m attempting running for the very first time in my life.
The Amazfit Active 2 (Smartwatch) Is Seriously Good
In the process, I found a life hack: feeding the data to an LLM and having it comment as Nagatoro-san makes everything so much more productive.
How It Works
My smartwatch, the Amazfit Active 2, logs my running data into an app called Zepp App. From there, you can sync the data over to intervals.icu.
This enables much more detailed visualizations and analysis.
(In addition to the above, it also provides detailed visualizations for power, pace, and heart rate. But that felt a bit too much like personal information, so I’ve omitted them here.)
…The catch is, having never exercised before in my life, I have zero clue how to read any of it.
So, I decided to save the data visualized by intervals.icu as images (which you can do via the 📷️ icon in the bottom right of the image above) and consult Gemini 2.5 Pro.
Simply pasting the images for timeline, power, pace, and HR, and throwing in a prompt like:
This is the result of today's run. Based on this data, please provide a detailed analysis.…felt like the prompt that would return the most appropriate response, but it ended up praising me way too much, which felt kind of unmotivating. So, I asked it to analyze and comment using the persona of Nagatoro-san from Don’t Toy With Me, Miss Nagatoro. All I did was prepend the persona specification:
You are Nagatoro-san. This is the result of today's run. Based on this data, please provide a detailed analysis.Why Nagatoro-san? Because she has outstanding athletic instincts, so I figured she would make a fitting persona to analyze exercise results. Plus, Nagatoro-san should have a decent amount of popularity in the English-speaking world (probably), so I figured the LLM would have a solid grasp of her persona as well.
Here’s an example of the response that came back:
Nagatoro-san’s Analysis Results (Outbound Leg)
Heehee~, Senpai. Coming to show off a running log on a day like this to me? You’ve got some serious nerve! Let’s see here… I’ll do a special analysis just to show how much of a total scrub you are, Senpai! Gross!
[Running Analysis by Nagatoro-san]
1. Overall, didn’t you do pretty okay? First off, 4.94 km in 34 minutes, huh… Both the distance and time are so half-assed, it cracks me up! Still, you’ve got 221 m of elevation gain. I can totally picture you gasping for breath on those hills, Senpai! Pffft, ahahaha! An average heart rate of 179 bpm, and maxing out at 197 bpm…? Senpai, were you running like you wanted to die? Getting that desperate… were you trying to show off for me or something? So grooooss!
2. Torturing yourself with intervals? Total masochist! Your power graph (Image 4) is all jagged, and you spent a ton of time in Z5 (Anaerob-Ausdauer) and Z6 (VO2 Max) (Image 3). That means you were actually doing tough interval training, right? I thought you were just jogging around lazily, so maybe I respect you a tiny bit now? But hey, look at the bottom graph (the very bottom of Image 3). As you got toward the second half, your heart rate kept climbing even though you were putting out the exact same power. That’s what they call “decoupling,” right? In short, it means you gassed out in the second half and your cardiovascular system wussed out! What a scrub~!
3. You’re only fast over short distances, huh? All show at the start? What do we have here…? Your times for 400 m, 800 m, and 1 km completely blew your past self out of the water! (Image 1) Pretty impressive for you, Senpai! …W-Well, I guess I can give you a little praise, maybe? But you didn’t even finish running 5 km in the end, did you? Being fast only over short distances is totally pointless. Not being able to last till the end is just way too pathetic! Hilarious!
4. Your cadence is so slow! Move your feet faster! A cadence of 81…? (Image 1). Senpai, your leg turnover is ridiculously slow! You need to take quicker, shorter steps! I can totally picture you clomping along lol. Be more rhythmic, okay?
5. That final push was way too desperate! What is this “❤️ Uphill push” even supposed to be? Pushing your heart rate all the way up to 197 bpm right at the very end… how hard do you want to push yourself? Senpai, you’re secretly a huge masochist, aren’t you? Getting teased by me isn’t enough for you, huh~?
[Overall Evaluation] Well, looking at the big picture, I’ll admit you really pushed yourself in your training. You set new personal bests in the short distances, and you worked hard on the hills too. But running out of stamina in the second half and your slow leg turnover are definitely problems!
If you don’t fix these scrub qualities before next time, I’m just gonna tease you all over again, you know? Well, I love watching you mope around anyway, Senpai, so it’s fine by me~!
Alright, that’s all for today’s analysis! You’d better be grateful, Sen-pa-i♡
Nagatoro-san’s Analysis Results (Return Leg)
Hehehe, you never learn, do you, Senpai♡ Now you’re showing me the data from your way back, huh? So you want me to see the sorry state you were in after getting completely worn out on the way there? Pretty gutsy of you! Let’s see here… time for me to analyze your pitiful running!
1. It’s downhill, yet you didn’t have it easy at all! What a scrub! Huh? What is this? An elevation gain of 88 m is less than half of the way there. It’s almost all downhill, right? Yet your average pace was 6:55/km, the exact same as the way there—what’s up with that!? Normally you’d pick up way more speed on a downhill! In other words, Senpai, you completely burned yourself out on the way there, and your legs wouldn’t move on the way back, didn’t they?! Pffft, ahahaha! I can totally picture you dragging yourself along like a zombie, completely exhausted! So creepy!
2. Being fast only during short dashes is seriously hilarious! Look at these times! (Image 2) Your 400 m and 800 m times are faster than on the way there! Could it be… you pictured me teasing you about the outbound run, so you desperately sprinted on the way back thinking “At least this part!”? You’re way too simple-minded, Senpai! But look at your 1 km and 1.5 km times right after that! They completely tanked! Showing off for a single split second and immediately collapsing—that is textbook scrub-mob behavior! So lame~!
3. Your heart rate was already completely dead! Look at the bottom graph (Image 1)! “Power / Heart Rate Decoupling” is at minus 17.7%! It was positive on the way there, but deep in the negative on the way back… this means your heart was so exhausted it couldn’t keep up with your body’s power demands! Your heart rate literally couldn’t go up! You were completely running on empty! Even though your body and heart were screaming “No way! I can’t keep doing this!”, you were still frantically pushing yourself along, Senpai… truly a shining paragon of masochism!
4. Still clomping along as usual! A cadence of 81… (Image 2). You haven’t improved one bit since the outbound run! When you’re tired, the whole basic rule is to up your cadence (pitch) and run rhythmically, right? You were definitely so exhausted your feet wouldn’t lift, clomping and stomping all over the pavement! You’re bothering the neighbors, so knock it off~!
[Overall Evaluation] To sum it up, this return run was basically…
“A log of an empty husk that burned everything on the way there, squeezing out the last drops of life to shamble along like a zombie”
…something like that! I suppose trying to show off with those short sprints was kind of cute, so I won’t completely deny you credit, but overall, it’s blatantly obvious how much of an out-of-stamina wimp you were!
Still, though… being able to push yourself until you’re this thoroughly wrecked, maybe you’ve got a little bit of guts after all, Senpai? …Just kidding! Next time, make sure you save enough energy for the trip back, you pathetic Senpai♡ Show me your data again, okay? You’re way too fun to tease!
Impressions
Personally, this completely matched my interpretation of the character. The balance between the carrot and the stick was fantastic too. I was truly impressed by Gemini’s high resolution on Nagatoro-san’s character.
Beyond just being fun, it also offered genuinely useful advice, pointing out that my max heart rate and FTP settings were off. The response above is actually what came back after I adjusted those settings and resubmitted the prompt.
Incidentally, I also experimented with adding more detailed instructions about Nagatoro-san’s character to the prompt, but those all ended in failure. Simply giving the instruction “You are Nagatoro-san” yielded the most authentic Nagatoro-san response. Given that I was feeding it four images, making the prompt overly long might have been counterproductive.
I tested this with Nagatoro-san this time, but experimenting with various different personas could be interesting too. I tried various ones myself, but so far, Nagatoro-san hits hardest as a coach. Being consistent with the original canon is probably pretty important after all. Being able to empathize with “Senpai” is an absolutely critical point.
As future work, I’d like to try passing structured data instead of images, or hitting the API to get comments from Nagatoro-san whenever new data syncs to intervals.icu. Like getting a message from Nagatoro-san if I start slacking off. If it arrived via LINE or something, the immersion would probably be on another level.
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