Step 1
First off, beat the main game on either Casual or Standard difficulty. Either one works, no need for harder modes here.

Step 2
Once you finish the main story, you’ll unlock the new mode called Unknown Signal. Jump into this mode, and Ada will lead you straight to a secret hidden area, where you’ll encounter the Large Ada.

Step 3
The Large Ada has a total of 10 simulation training challenges for you. But note that not all 10 are unlocked from the start — only 6 are available at first. Until you clear those initial 6 challenges, the cable car to other zones is locked. You can only head back to the protection station or stay inside the hidden area for now.

Step 4
After completing the first 6 simulations, the cable car will finally be accessible. You can now travel to other areas and take on enhanced version bosses. Every enhanced boss you defeat will unlock 1 extra simulation challenge. Once you’ve beaten all 4 enhanced bosses, the last 4 training challenges will unlock all at once, letting you complete the full set of 10 simulations.

Step 5
Finish all 10 simulation trials and claim all your rewards. One reward is super important here: a key module named Black Box. This item is mandatory — you literally can’t trigger the secret ending without it.

Step 6
Before you start the final boss fight against Number Eight, make sure you equip the Black Box module beforehand. Skip this step, and you’ll lock yourself out of the secret ending entirely.

Step 7
Keep the Black Box equipped, defeat Number Eight, and complete the final chase sequence. You’ll then reach the end credits. Once the credits finish rolling, a hidden surprise menu will pop up — that’s your confirmation you’ve unlocked the secret ending!

Final…
Hope this walkthrough helps you all get the secret ending easily! If this guide worked for you, don’t forget to leave a like and bookmark this post for other players to find too!