Universal Tower Defense Z: How to Find All 4 Puzzle Pieces for Secret Isagi

Secret Isagi is an unlockable Blue Lock unit in Universal Tower Defense Z, and it does not come from the standard summon banner. Instead, you earn it by hunting down four hidden puzzle pieces placed around the game and finishing Isagi’s trial. The reward mirrors Isagi’s own “puzzle” theme from the anime, where each piece has to click into place before the picture is whole.

Quick answer: Find and interact with all four hidden puzzle pieces spread across the lobby and event areas, complete Isagi’s trial quest, and the Secret Isagi unit is added directly to your inventory.

What you need before starting the Isagi puzzle

The puzzle chase is a lobby and quest activity, not a wave you fight through. You interact with objects placed in the world rather than rolling for the unit, so no gems or trait rerolls are spent. Because it is tied to the Blue Lock content in Universal Tower Defense Z, make sure your game is fully updated to the current version before you begin; otherwise, the puzzle pieces and the trial may not appear.

Load into the game through its official Roblox page and let the lobby finish loading completely before you start searching.

Open Universal Tower Defense Z on Roblox

How the four puzzle pieces work

All four pieces are hidden away from the main path, so they take deliberate searching rather than passing by them. Each one is a separate collectible you have to walk up to and interact with. The order you grab them in does not matter, but you must register all four for the trial to recognize your progress.

Move around the lobby with WASD and check the edges, corners, and raised areas where a piece can sit out of the normal sightline.

Walk directly into each puzzle piece and press the interact prompt to pick it up. The piece should disappear and count toward your total once collected.

Repeat until you have secured all four. Keep track of how many you have grabbed so you do not waste time re-checking a spot you already cleared.

Tip: If a piece will not register, back away and approach it again so the interact prompt reappears. A piece only counts after the pickup actually triggers.

Completing Isagi’s trial to unlock Secret Isagi

Gathering the four pieces is the entry requirement, not the finish line. Once you hold all of them, Isagi’s trial quest opens up. Finishing that trial is what actually hands over the Secret Isagi unit.

With all four pieces collected, start the trial from the quest prompt tied to Isagi.

Clear the trial’s objective to the end without leaving early, since exiting midway can drop your progress.

Confirm the completion when the game prompts you. Secret Isagi is delivered to your unit inventory as the reward.

How to confirm you unlocked it

You know the process worked when Secret Isagi shows up in your unit list after the trial ends. If the unit is not there, the most common cause is an incomplete piece count, so re-check the lobby for the piece you missed and make sure each one triggered a pickup before you started the trial. Leaving the trial before it finishes will also stop the reward from being granted.

Once Secret Isagi is in your roster, you can place it like any other unit and slot it into your team. From there it behaves as a standard collectible unit, ready for Story Mode, Blitz farming, or event raids alongside the rest of your lineup.