The short answer, and the one source under it
Every area stays reachable and free roam continues after the story, so the collectible sets are not gated behind chapters you can walk past. That is PowerPyx's position from its own playthrough, and it is why `/collectibles/` is built as a completion tracker rather than a per-chapter checklist with warnings on it. It is one source. It is a source that finished the game, which is more than the wikis publishing missable lists can say, and it is also a source whose headline collectible total and category breakdown disagree with each other by eight — so it is cited here for the rule and not for any number. What follows from the rule is the useful part: if you are looking for a list of things to grab before a door shuts, the reason you cannot find a good one is that the game does not appear to have those doors.
Four things filed under “missable”, sorted by what is actually at risk
Three of these cannot cost you anything on a careful first run. The fourth can end the run outright, and it is the one no competitor page on this query lists.
- Can end the run
The Foreman wheel in the Ogouchi Buffer Zone subcity
Evidence · Two players, one thread, no developer reply
- Published, not corroborated
Documents, key items and fast-travel points in Reincarnation+
Evidence · One wiki table, no stated method
- Not losable by design
Blade Collector, and the twenty-first blade
Evidence · Two wikis that do not cite each other
- Cannot be lost
The collectible sets — blades, documents, camps
Evidence · One playthrough, and it contradicts itself on the totals
- Can end the run
- Published, not corroborated
- Not losable by design
- Cannot be lost
Sorted by risk, not by how often each appears on other sites — which is close to the reverse order. The source count beside each verdict is the point: the most dangerous row is also the thinnest-sourced, and both facts are printed rather than averaged.
Why external trackers exist anyway, and it is not missability
The in-game map only shows what Koo has already smelled. Points of interest appear when the dog picks up a scent in range, and anything outside that range never appears at all — so a region can read as cleared on your own map while still holding pickups. That is the actual reason this game has a tracker economy, and it is a different problem from a missable: nothing has been lost, it was never displayed. It also means "I explored everything and the map is clean" is not evidence of anything, which is the one piece of advice on this page that changes what a careful player should do.
- Some categories tick themselves off in-game once taken, and a few sets can be audited from the inventory screen. Where that works the game is a better tracker than any website, this one included.
The achievement that cannot be finished in one run, by design
Blade Collector asks for every blade, and the twenty-first is the Kanzashi, which is handed over at the start of a new game plus and cannot be obtained on a first run. Two competitor wikis that do not cite each other agree on this — Fextralife places it at the start of Chapter 1 of NG+, Game8 lists it among the post-game rewards — and that overlap is the strongest corroboration available on any claim on this page. Read carefully, this is not a missable at all: it is not something you can fail to do, it is something the game will not let you do yet. No amount of care on a first playthrough changes it, which makes it the opposite of the advice a missables list is for.
The thing that can actually end a run, which no guide site lists
On the way to the Foreman in the Ogouchi Buffer Zone subcity there is a wheel. Turning it opens a hatch down into the subcity. Two players report independently that if you leave the area before going through that hatch, it is shut when you return and the wheel is permanently non-interactive. Nobody has published a reload procedure, an earlier-save route, or a confirmation that the run is recoverable, and the developer has not replied to the thread. This is the only point of no return on this site with evidence behind it, it is a progression blocker rather than a collectible, and it appears on no competitor's missables page — including the ones that rank first for the query in two languages. If you turn the wheel, go through the hatch on the same visit.
- Two players, one thread, no developer reply, no workaround — that is the whole evidence base, and it is thin. It is published because a thin report of a run-ending bug is worth more to a reader than a thick list of things that cannot be lost.
The nearest thing to a real missable is a new game plus rule
Game8 publishes three things that do not carry into Reincarnation+: key items such as the Red and Yellow Keys, unlocked fast-travel points, and documents. The documents exclusion is the one to read twice if you are chasing completion, because it means the Know-It-All set is re-collected on every run rather than banked. That is one wiki's table with no stated method and no per-claim provenance, so it is graded here as exactly that — the independent launch-build source covering NG+ is silent on all three, which means this is published rather than corroborated. It is on the page because a completionist planning a second run is the person most likely to be hurt by it being wrong in either direction.
Where this page could be wrong
It cannot prove a negative, and the shape of the gap is worth naming precisely rather than hiding behind a confident answer. Nothing published establishes that any blade is missable — but that is an absence of evidence and not a guarantee, and no source has addressed it either way. The same hole sits under the boss roster: this site's chapter order comes from one run corroborated by unlock rates, and a fight that was optional, missable or simply skipped by that player would not appear in it at all, with nothing published that would reveal the omission. So the honest form of the answer on this page is that one player who finished the game says areas stay open, no player has reported losing a collectible, and one specific sequence has hard-blocked two people. If a real missable exists, the evidence for it has not been published yet, and this page will say so on the day it is.