The game tracks them as one objective, so treat them as one errand
The quest tracker lists the three keys as a single block and ticks them off individually, which is the clearest statement anyone has of what the set is for: the three together open the gate toward the Nushi’s Lair, and Chapter 1 does not continue until all three are in. Only one of them is handed to you on the story path. The other two are out in the world, and the two published guides covering them do not fully agree on where.
Which one are you missing
Tick what you already hold and the strip says what is left; pick a key and its route opens underneath. Where the two guides give different directions, both are shown with their names on them rather than merged into one confident sentence — that is not hedging, it is the actual state of the evidence, and following an averaged instruction to a place neither source described is worse than knowing there are two candidates.
The quest tracker lists “Obtain the Red Key.”, “Obtain the Blue Key.” and “Obtain the Yellow Key.” as one objective block, ticking each as it lands. The three together open the gate toward the Nushi’s Lair, which is how Chapter 1 continues.
Still to find: Red Key, Blue Key, Yellow Key.
Lying in front of a broken golem on a raised platform. This is the one the guides describe differently.
From Nobody hands it over. It is a pickup beside a dead golem.
- Head for high ground away from the Subcity 03 entrance and look for the platform with the plume above it.
- Both guides agree on the destination: a broken or dead golem, with the key on the ground in front of it.
- Both describe getting up there by traversal rather than by a door, so it reads as a climb rather than a gated route.
The two guides disagree
Video Games Chronicle puts it at the Lookout Shack, reached by crossing the ruined buildings in the drowned section on the map’s north-eastern edge.
Into Indie Games puts it “just east of the Subcity 03 entrance”, spotted by a plume of red smoke rising off a high platform and reached using Emma’s hair.
These may well be the same place described from two approaches — a campfire named Lookout Shack does exist and is on this page — but nothing we hold proves that, and “north-east across the drowned ruins” and “just east of the entrance” are not the same instruction to follow. If you have stood there, the contact route is on the site.
Tailwater KeyNot a gate key
Not a gate key. It drops from the elite in the Tailwater cave and opens a door in that same cave.
What is behind that door is the disagreement above: the room with the Yellow Key golem, or a separate room of valuables. Every source agrees on where the key comes from, and none of them agrees on what it is for.
The Lookout Shack exists, which is one thing the dispute does not turn on
One of the two guides names the Blue Key’s location as the Lookout Shack and the other never uses the name, describing a high platform east of the Subcity 03 entrance instead. A campfire called Lookout Shack does exist — it is in the walkthrough capture, with the standard rest menu on it — so the disagreement is about which landmark to steer by, not about whether one of them is invented. What nothing establishes is whether the platform with the smoke plume and the shack are the same place.
What we could not check, and one dead end worth recording
Two English videos that look like sources for this page are not. The walkthrough this page takes its two frames from has a caption track that is a machine translation of the game’s Japanese dialogue, and it renders the three keys as “red, blue and wood” — usable for stills, useless for quotes. A second location guide is spoken in Italian with a caption track under 1.5KB. Both were captured and discarded rather than quietly leaned on, which is why this page cites written guides for its routes and video only for what can be seen in a frame.