BO3 Zetsubou No Shima Seeds Of Doubt Easter Egg can do on SOLO or CO-OP.
First, build KT-4, Zombie Shield, Upgrade KT-4, Get Skull Of Nan Sapwe and finish your challenges. For more details on how to do those, Click this link for KT-4, Zombie Shield, Upgrading KT-4 and Skull Of Nan Sapwe
First, Head over to the Living quarter. Then go all the way to the end corner where you can get Purple water (115). On that corner you will see a poster. To reveal the other half, use your Skull of Nan Sapwe then press hold right click mouse to mesmerize and aim it to the poster until you see the other half. Next, run towards near the bunker entrance. On your right use the skull same procedure as how we did on the poster. This time a secret room will reveal and once you go inside, your character say that you need to find the missing part.
Second, Go on the challenges area then wait for the lightning to strike. Once the place are electrified, Pick up your shield and run towards.
For Solo part, go on the zipline. For me, i used Lab A. Once you are in that place, use your electrified shield and electrocute the panel. Then, quickly use the zipline. This is the hardest part. Once you are in the area of platform, quick spawn your buttons in order for you to be released. Then look and pick the part ( Gear ). Note: Make sure you will not going to miss the spot or else you will die if you drop before the platform.
For Co-op part, This need a timing and coordination. One player must have electrified shield, then head towards to any end of the zipline and get the shield ready. The other player must use the zipline, Once he is zipping this player must communicate to use the shield to electrified the panel at the certain time. Thats the only way for that player to be drop. Note: make sure you drop on the platform, if you drop before the platform. You will die.
Third, This time you just need a gum called “Anywhere but here”. If you don’t have that in your inventory. You have to re start the game and load that up. Once you have that gum, use it and you will teleported on a secret room. This room is small so its easy to find the part. The part is just on the floor.
Fourth, Missile. To get this, you need to plant then, water it with blue plus one shot of your KT-4 for additional recipe. You have to do this three times, this means that you have to do this once in every round. Note: If you miss once, you have to re do this again.
Once you have the missile, head towards to Anti aircraft platform and place your missile to the canon. Wait until the plane comes in. Before you fired up, make sure you aim it right because if you miss. You have to start again on planting a seed. Once the plane explode, look up and you will see a small parts that has a smoke dropping. This will give you a hint on where this part landed.
Bring all the part where you open the secret door and place it. Now that all parts are in place, elevator will open and ready for the boss fight.
Boss Fight, Before you go down make sure you have a new shield, new mask and optional of new pack gun. Once you are in the basement. There are some blockage on the way. To get this out, you need to shot those glowing orange with upgraded KT-4. Once you reach the door. You will see another glowing orange. Shot that and the fight will start. In order to kill the boss, wait until you see a glowing orange on his hand. This will take four times to finish him, but the only gun that will work is the upgraded KT-4.