Cultivated from the "Legendary Tree" brought back during the cherry blossom viewing it has the potential to help defend Nazarick. Demiurge and the others have decided that a stronger magic tree would be needed to put it to practical use, and begin to secure the magic tree.
At the Enhanced Treant test site near Nazarick, Demiurge showcases to the protagonist his cultured treants that he developed using the sample of the Supreme Odor Flower given to him by Momonga from when they acquired the said tree for the cherry blossom viewing. From his research, he has determined that the "Supreme Tree" that he brought back to Nazarick was not a result of contamination but a naturally occurring specimen. In addition after repeated efforts in breeding and culturing he finally found a practical application for the treants to contribute to the Great Tomb of Nazarick's defense. He managed to train the treants to follow orders.
Demiurge is informed by Abyss Demon that two human bandits have stumbled close to the test site, Demiurge decided to demonstrate. The demon interrupts the two thieves in the middle of an argument. Though taken by surprise they deem him to be an easy mark due to his clothes, to their shock they are easily incapacitated and dragged to the test site. One of the thieves tries to bribe the demons offering him the money from their hideout but is quickly silenced. Demiurge has Abyss Demon place the unconscious man next to an Enhanced Treant and orders it to take the left arm off first to which it complies and begins to absorb the human. On the next human, Demiurge as the treant drains its prey, demonstrating that no matter how much its prey cries it will only obey those from Nazarick.
The protagonist finds this development impressive and reasons that if the Enhanced Treants are planted around Nazarick, it will decrease the amount of manpower needed to defend the dungeon. While the area that Demiurge has tested is small, the two decide to take it to the next phase and present it to Momonga.
Upon hearing the results, Momonga is thrilled at the news of the project. However, he asks if there are any issues that may arise. Demiurge states that while normal humans are easy to be dealt with, the same cannot be said for adventurers that might appear, but nonetheless that should not be a problem. Since the treants have no real intelligence they cannot send warnings via [Message] however they can signal incidents by shaking their branches to alert personnel. However, at most three treants can connect with each other via their roots. In order to centralize an effective defense network, Demiurge believes a command tower is necessary for the security network.
The only thing he believes that will serve as an effective command tower would be the "Supreme Tree" which will receive all incidents and reports from the other treants. Momonga remembers in a previous report that there was a high possibility that the tree they acquired was not the actual "Supreme Tree" but an offspring. Thus the real "Supreme Tree" that is spoken in legends and stories in E-Rantel must be still out there. Demiurge asks permission to conduct a search for the tree which Momonga grants.
Demiurge gathers Aura Bella Fiora to join him on this mission. Knowing that their destination would be the Great Forest of Tob, she suggests they request Hamsuke to join them on this mission. In addition, Slimeko and the protagonist join due to their previous handle of the Supreme Tree's offspring. Heading to the forest they meet with Hamsuke who is now managing a village of goblins and ogres. Learning that they wish to find the Parent Tree, Hamsuke guides them back to the Forest of Death for clues with her demi-humans providing support. However, no clues can be found and Demiurge admits that it is unlikely that an offspring from the Parent Tree would be close to it's offspring. From his studies of the Enhanced Treants that were a result of his experiments with the Supreme Odor Flower, there are two possible ways that the Parent Tree dispersed its seeds, one is the method of planting and transporting them to the living organisms. The second are that the seeds themselves can fly. He had observed that the enhanced treants possessed seeds which they can shoot as projectiles, but also possess wings to allow them to fly on the wind. The Floor Guardian hypothesizes that the Supreme Odor Flower's seed came north using the northern wind from the Azerlisia Mountains. He believes at most a few kilometres is the range of the seeds and with the ogres and goblins they will eventually find it, though they may lose some manpower.
Hamsuke reports to that nothing has been found, though a couple of her ogres have gone missing. While they could have gotten lost, Demiurge has Hamsuke send a search party for them. The search party fails to return prompting the group to search for themselves. Hamsuke take the lead to the site where the ogres vanished, but is stopped by Aura as she notices that one of the dead trees is actually a treant. It's guessed that ogres were eaten by the plant. Demiurge thinking they finally found a clue wishes to examine the treant before confirming the Parent Tree is here. Aura attempts to sneak behind the treant only for it to attack her with its roots. Observing the sly tactic and the Demiurge takes to the air in his Imp for and see a large tree in the distance, confirming they have touched the edge of the Parent Tree's security. He is nearly hit by a projectile coming from the Parent Tree, and Demiurge realizes that the Parent Tree has already received an advance warning of intruders from the treant below.
Returning to the ground he informs Aura and company of the widespread defense network around the Parent Tree. Even if they ignore all the treants and charge from the air, they would still be under intense attack tree's defense network. Added to the seeds that contain neurotoxins that can be a hassle. Knowing they could not capture the Parent Tree with the current strength, Demiurge then returns back to Nazarick to retrieve Cocytus. After getting approval from Albedo, Demiurge orders the Pleiades to make preparations for another cherry blossom viewing as now that the Parent Tree has been found they could give their master Momonga a "normal ceremony".
He and Cocytus return to the forest where Cocytus pledges to assist. He had be vital in defeating the previous tree, however Demiurge insists this time they will bring the Parent Tree alive. Once Cocytus weakens the tree enough, Demiurge prepared a special substance that will induce the tree into a deep sleep and will be safe to transport back to their territory.
The group then approach the tree and finally behold it sight and its surrounding treants. Cocytus then begins the attack by using [Frost Aura] to freeze a portion of the treants around the Parent Tree, which are then shattered by a follow-up attack of [Cutting Wind]. The remaining treants then begin to launch a barrage of seeds at the Floor Guardian. Demiurge transforming into an Imp approaches the Parent Tree while flying low through the opening opened by his friend to avoid the barrage of seeds. He then casts [Hellfire Wall] around the Parent Tree, separating it from its thralls.
The treants outside the circle, attempt to reach the Parent Tree, but they are stuck in the fire. Aura using a vial given to from Demiurge, containing an opiate extract from the Enhanced Treants, drops the contents around the Parent Tree. The liquid permeates in the ground, causing the treants that have already been damaged by the fire to lose their power and fall to the ground. Demiurge then grabs Cocytus and together they fly into the inside of the Hellfire Wall.
Most treants were cut out due to the fire, a few treants remain in the entrapped area. Demiurge asks Cocytus to prune the area while he casts [Hellfire Wall] and [Aspect of the Devil - Hellfire Mantle]. Despite his attacks the treants intensify their attacks. Cocytus then takes the lead and cuts through the treants that try to block him. He is assisted from afar by Aura using [Sky Eye]. Cocytus finally reaches the tree and uses [Vidyārāja Strike], knocking the Parent Tree to the ground. He halts as Demiurge then injects the tree with an ultra-pure anesthetic.
The tree now their's, Demiurge calls Mare Bello Fiore to ask how are preparations for the Parent Tree's new home. The dark elf reports that everything is prepared. This pleases Demiurge at the site will not only be the location of the Parent Tree's central command hub but also the venue for Nazarick' "normal cherry blossom viewing" were they will celebrate the establishment of the new defense network.
Back at Nazarick, preparations for the announcement party were approaching in the middle stage, and the costumes were being prepared. Sebas Tian notices the costumes that Narberal Gamma is preparing and asks if this will be for the party, which she confirms. He asks about the details of the costume, which Narberal states that the costume is suppose to represent "loyalty" and "justice". This piques Sebas Tian's interest but when he finds out that the costume will be worn by Demiurge he believes it to be a mistake.
Hamsuke helps move the Parent Tree through the forest via [Floating Board]. Demiurge and his allies then depart from Hamsuke, when they, arrived at the installation site near Nazarick. Lowering through the hole that Mare dug with his magic, connecting to a cavern underneath the grassland, the Parent Tree is installed in a large hole in the ground. There it is planned to have the Enhanced Treants roots will connect with the Parent Tree to create the defense network. When Mare closes the ceiling, he inadvertently disturbs a couple of Forest Worms underground. After the Floor Guardians dispatch them, Demiurge states while they have all they need, the defensive network pends on the cooperation of the Parent Tree. So in order to earn its loyalty, Demiurge will educate it to be obedient. He then proceeds to give the Parent Tree the antidote.
Upon regaining consciousness the Parent Tree proceeded to bloom. While Demiurge comments the sight to be worthy of praise he soon understands the effect to be more insidious as the plant seems to have the power to attract and charm the surrounding monsters. Several worms emerge from the wall and the Parent Tree spews out pollen that seems to enhance them. Demiurge excited at this display decides to thoroughly teach the tree who stronger so that it will never again resist. With that all the worms the Parent Tree had summoned are destroyed save one. Demiurge not wanting to deal with it orders the Parent Tree to get rid of it. The tree upon realizing its situation and difference in strength, immediately kills it. Demiurge then tells the tree to bow, though it is initially confused by the order. When ordered a second time it does by lowering its boroughs.
Not satisfied with its show of loyalty, Demiurge openly states that that the tree is of little use to defend Nazarick. He promptly orders Cocytus to starve the tree by freezing it. Upon hearing that, the Parent Tree then slammed all its branches to the ground, literally lying down and expressing its submission, which finally pleases the demon in that he has broken the tree's will.
Later in the cavern which has been decorated with lanterns and filled with tables full of food, Momonga while happy about the defense network is trying to enjoy himself. Though the ghastly decor of the Parent Tree and Demiurge's latest piece of furniture make it hard for him. Still to keep his subordinates happy he spreads out praise for their work.
Demiurge as the man of the hour comes dressed in a outfit called a Chivalrous Costume to display his loyalty to Momonga. However to his surprise he finds Sebas Tian also is wearing one, who insists that the costume reflects justice and helping the weak. The two are broken up by Cocytus as they are before Momonga. To change the subject, Momonga asks Demiurge how he came up with this event. For the party Demiurge explains that it was to present a Yozakura, night cherry blossom which is all the time considering they are underground in perpetual darkness to give Momonga a normal cherry blossom viewing. Momonga congratulates despite not knowing anything Demiurge says leaving the party as a success.