I imagine I'm not adding anything substantial to the conversation by saying this, but the art is gorgeous. The backgrounds establish the mood of each scene perfectly, and the bear's character design is tastefully muted perfection, recognizable and distinctive without being as so flashy it would clash with the low-key tone of the story. I like it all a lot!
The custom UI is neat, but not without its problems – e.g. the LOAD button in the title screen has deeper shadows than the rest, various clickable things don't have hover effects – and looks somewhat incohesive as a whole? All the menus are fine by themselves but kind of in their own style, I'd say, and the default font of Ren'py doesn't really match the playful look of much of the other stuff. Regardless of the cool ideas, the art direction doesn't quite come together. (And while we're here: it's a shame that the itch page doesn't really reflect the look of the game.)
The prose has its moments of dazzling imagery, and the vocabulary is very good in general, but it does come off as kind of wordy and suffers from some recurring editorial issues. There's a lot of repetition that feels awkward to me. Some examples: "hours he spent in the faculty, and while I don't remember the exact amount of time he spent", "pursuits other than the pursuit of more money", "won't get repacked any faster if I try to stop you from packing". Sometimes the writing reiterates a thought, too, like here: "There's a comfort in not needing to say anything, to understand that everyone present is focused on the same task, no words needed."
There's also just the occasional line that could afford to be tightened or broken up for the sake of flow: "We just spent long days under the sun, our rods the sole impacts in the still waters until that fine moment when the tranquility broke in a sea of tension." Maybe this is just me, but I'm not crazy about the part following "when the" – feels too structurally complicated, could rephrase to something like "fine moment of tranquility breaking". And while not every instance is an objective punctuation error, there are a lot of places where I'd insert a comma for the sake of clarity. (As a smaller nitpick, the game appears to use normal hyphens everywhere instead of en or em dashes: "I wasn't the designated driver-I was drinking just as much as them-but...")
As far as voice goes, the bear's dialogue sounding formal and flowery works for the character, but some of that slips occasionally into the first-person narration and the fox's speech. There's also just a couple of isolated instances of the game using 2nd person ("He sighed as you started funneling the lures into his bag", "His laughter is almost contagious, but you're not ready to just let go just yet"). There's a clarity of purpose to everything, but strategic edits would help a lot to make the prose just a little bit punchier, smoother, and snappier.
Plot-wise, the opening segment is a lot of fun, but the label "demo" doesn't feel like a lie, since the story doesn't really go anywhere yet. I guess it's an inevitable consequence of approaching the medium with this much ambition. The art is lush with details, and there's more of it than in some completed VNs – completing the project with this much fidelity in just one month would have been a lot to ask.
All in all, What He Carried is a decent read for what it is, i.e. largely setup for payoffs to presumably come. The art is stunning, the rest could use more polish; still, not a bad start at all.