"CP 1765, October 7. 88 days have passed since landing. Local time: AD 2016, November 13."

  "Min is still bothered by what happened four days ago. But honestly, expecting me to spend all day with that fox without resisting? That's just plain unfair. I don't think it's that hard to understand, but he clearly can't grasp why I hate the fox he keeps. Just another 'cultural gap'."

  "Resistance seems hopeless. Even though I sleep in a gas mask every night and feign illness, he shows no signs of concern. He insists, 'You'll get used to this life — lots of people keep foxes as pets.' I know wild foxes are common on Earth, but this is outright mockery! Classic shameless self-interest. Who knows when he'll find someone else to take the fox? Anyway, it looks like I'll have to try to adapt to life with a fox — it's torture in disguise..."

  "So I can't help but ponder this again: how difficult is it for different intelligent species to coexist? We share enough similarities with them, both physically and culturally, yet we still clash over these bizarre matters. How much more so must it be for species with far greater differences? Technology can bridge physical gaps, but what bridges cultural ones?"

  "These are serious questions — perhaps an unexplored branch of sociology, or more likely falling within philosophy's domain. I'm no philosopher, but who else can answer them? If I ever return, I'll make sure to submit a satisfactory report on this..."

  "Finally, regarding the weather, it has been four consecutive sunny days. Conditions have steadily improved since the snow stopped. Honestly, it's a shame I never got the chance to make a snowball during all that snow. Now it's too late for that."

  ***

  "Do you see these two squares as the same colour?" Min asks Xi P, pointing to an image on the computer screen.

  "No." Xi P replies simply. Though countless thoughts flash through his mind when he sees the image and hears the question, all that comes out of his mouth is just a simple "no".

  Min nods and logs the result in the text. The image he's showing is the famous "checkboard illusion", depicting a grid of black and white squares. The squares marked A appear darker than those marked B, though they're actually identical shades of grey. This is a minor illusion caused by the compensatory mechanisms of the human visual system. Fascinating that the same phenomenon can be replicated in an alien being.

  Well, probably. Last time, Xi P mentioned their colour vision was complex, and they discussed it thoroughly before starting the checkups today. Xi P tried his best to explain, but communicating technical terminology remains challenging. Min gets that they possess four colour receptors yet only experience trichromatic vision. The fourth receptor affects some kind of balance distribution, and its phenotypic distribution varies across different ethnic groups. Xi P ended up complaining about how much trouble this causes when designing screens for the electronics industry.

  Anyway, setting the colour perception aside, that this illusion worked is pretty much expected. A visual system that functions like a physical photometer doesn't align with biological needs. Incorporating appropriate compensation to aid object recognition is how normal organisms should be — at least in theory. After all, research into whether such illusions occur in animals has only begun recently, and Min has heard that designing the right experiments is notoriously difficult...

  As the scene suggests, Min is studying Xi P. Though Xi P should soon be preparing for sleep according to schedule, how could Min resist the fascination of researching an alien? In many ways, conducting various tests on Xi P and observing his reactions proves far more engaging than the microscopic studies in the lab.

  Moreover, Xi P is the most cooperative... non-human subject Min has encountered. Though Xi P consistently maintains a displeased expression — a stark contrast to Min's enthusiastic demeanour — consent is still consent.

  Most of the preceding examinations have focused on the alien's visual system. According to Xi P's own explanation, while their hearing is acute, they are fundamentally visual creatures like humans, rely primarily on information from their eyes to perceive the surrounding world. Differences in eyeball structure enable them to see in environments too dim for humans, though their visual acuity suffers slightly — meaning things appear somewhat less sharp to them. The difference isn't huge, only noticeable after checking using an eye chart.

  Unlike many nocturnal creatures on Earth, however, their eyes struggle to adapt to bright light — likely because their equivalent pupils can't constrict sufficiently. Directly staring at the sun is out of the question, and even the reflections off many natural objects in intense midday sun are too bright. Thus, sunglasses are essential for them during daylight hours. Beyond the pupils, there are likely other reasons, but the more in-depth explanations involve technical terms that are difficult to grasp.

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  "Honestly, the more I examine you, the more I feel we're actually remarkably similar. On the microscopic scale, it's all about DNA and proteins. You've seen it on the macro scale too. It's the intermediate scale where the differences are most pronounced. Truly baffling." Min remarks.

  "On the macro scale, I can't say for certain. It might simply be that, our planets' gravity and other data are similar, so the best evolutionary path was just that one." Xi P replies.

  Min acknowledges this, then suddenly realises something: "Wait, if that's the case, do you mean you have discovered other intelligent life forms in your mission?"

  "No, I'm just making an guess. Since our... um... interstellar exploration mission began, we have discovered several instances of early, primitive microorganisms. Oddly enough...eh, ra..."

  "What's odd about them?"

  "Their genetic material is either DNA, RNA, or some other similar substance. Like you said, I also believe there should be other genetic information carriers should exist. But maybe we're just, overthinking it." Xi P tilts his ear, equally puzzled.

  They can't immediately fly to other planets for sampling verification, so the topic ends there. After testing vision, Min plans to examine the tuefue musculoskeletal system next. Though it currently appears very similar to Earth creatures, who's to say there won't be any unexpected surprises?

  Besides, he genuinely wants to gauge the threat level of this alien predator living right beside him. Is it like a lion or tiger? Though its weight suggests it's closer to a cheetah...

  Shaking off images of alien creatures slaughtering humans, Min asks: "So, what about your sprinting records? In the best case, how long would it take your kind to run 100 metres?"

  "Hold on, I need to convert that."

  Xi P narrows his eyes, pulls out his phone, and after fiddling with what clearly looks like a calculator app, gives an answer: "Our world record should be around 7 to 8 seconds. Your 100-metre distance isn't a whole number for us, so we don't have a record for that exactly. I don't recall our exact time either, but it'd be in that range."

  Min clicks his tongue, slightly taken aback. He has never seen Xi P sprint at full speed, so though he always assumed tuefue excelled at short-distance bursts, this actual figure still surprises him: "Wow, our record is still over 9 seconds. By human standards, that's unbelievable. How do your kind achieve such a speed?"

  "That's a difficult question to answer. I guess you want to know how it differs from humans. Let me show you..."

  Despite his words, Xi P doesn't suddenly start darting around the small room of just over ten square meters. Instead, he begins fiddling with his own laptop. Soon, a 3D model of tuefue's muscular skeletal system appears on the screen. Signalling to Min not to look at the display yet, Xi P first leads him to the bedroom. They sit on the bed, and Xi P extends his right leg.

  "Feel my leg — here, the muscle between the first and second joints. Describe the sensation."

  "Uh... sure."

  Unlike humans, Xi P has two "knees" on each leg, divides the legs into three segments, as well as an ankle-like joint. The segment Xi P indicates isn't quite the thigh, nor exactly the calf — perhaps should be called mid-leg? Given Xi P's usual aversion to physical contact, Min hesitates before tentatively reaching out, to feel the muscles beneath the fur.

  "It feels like high-density rubber — tough yet elastic. Very firm." Min describes.

  "Try the upper and lower legs now. Compare them." Xi P urges him to continue.

  Honestly, touching someone else's leg feels downright strange. Min keeps himself from blushingby constantly reminding himself that this is closer to a medical examination and that he is only touching the leg. Moving along its length, Min continues his description: "The upper and lower legs feel more like ours. The muscle density feels completely different from the middle part. So, what's with that middle part? Is it a specialised muscle structure?"

  Xi P explains: "Pretty much. The muscles in our mid-leg part, has go, went extreme evolution. It's a kind of... non-voluntary muscle, rich in... wait let me check the word... fascia. It maintains a natural contracted state. It requires coordination with upper and lower leg muscles to fully stretch or relax. When fully stretched or relaxed, it... generates strong tension in the opposite direction."

  This broken speech is enough to give Min a splitting headache: "I don't quite get it."

  "Try, use your hand, pull my leg straight, then bending it completely."

  Min complies, slowly straightening Xi P's right leg before bending it back. He feels nothing unusual.

  "Do it faster. Slow motions won't trigger it."

  Min quickens his pace and soon notices the middle section produces a spring-like effect when bent or straightened: "Like a spring?"

  "Yeah. I remember seeing a kind of sport equipment like this here — extended metal attachments for the legs that make one walk with a bouncy motion. What was it called?"

  "Jumping stilts?"

  "Right, like jumping stilts. Our legs naturally have a similar structure, allowing us to leap like we're jumping during full-speed running. And, you've had enough of touching, haven't you?"

  Min quickly withdraws his hand and changes the subject: "I see. So those red markings in the 3D model represent these muscles?"

  "Yes. Besides the legs, they're primarily distributed in small quantities along the back. The speed difference mainly stems from them. Macro-wise, our tuefue musculoskeletal structure isn't very different from humans. I suspect our tissue recovery, bone resilience, and strength also differ, but those are secondary factors."

  "Interesting... Um, and, I don't mean to offend, but from what I gathered, when I touched you earlier, the way your ears relaxed and flattened against your head... does that mean you enjoyed it?"

  Xi P merely shoots him an icy glare in response.