Shau reveals that sometime ago, Sandros and his Scorpiss terrorized their planet and turned it into a wasteland.
Mari appears and leads them to their base where she revealed that Child Baltan from 10 years ago was the one that brought her to this place. Musashi encountered him earlier in a dream where he got destroyed by Jin. Once arrived, they were introduced to Alien Gyashi, where their leader, Jin, holds a dislike towards humans for being selfish. Soon the Team SEA follows Shau and Reija to their hideout where a portal opens, leading to her people's hideout.
Scorpiss retreats for a while and the mermaid reveals her name as Shau while telling Musashi that Mari is with her people. However, all he foreseen was a dream and realizes that Cosmos will never return. The phantom-looking Ultra rescues Reija and overpowers Scorpiss while destroying it with the Blazing Waze. Musashi takes his Cosmo Stone and transforms into Ultraman Cosmos Skeleton Corona Mode. There, he witnesses the mermaid, now having human legs fuses with Reija, turning the monster stronger but still, overpowered by Scorpiss. Musashi exits the TROY BS and brings his friend to safety. Reija appears and fights the monster but only to be overpowered by the menace. Once they about to be killed, Team SEA fires a missile, bringing it away from the hospital. As the monster is rampaging in the city, it begin to destroy a hospital that Musashi's friend resides in. Musashi is joined by Team SEA and they launch their TROY AS and TROY BS. Musashi recognized him earlier for turning Juran into a barren wasteland and killing Parastan. They were interrupted by a warning where a monster named Scorpiss was entering the Earth's atmosphere. Musashi was taken to their base and revealed that the monster he encountered earlier was Reija, who was detected undersea a year ago. Then, Koji, an original member of SRC and now a captain of Team SEA approaches him as he is glad that he survived. He awakens at the hospital as his friends visits him but Mari was nowhere to be seen. The man decides to eliminate Musashi for interfering with them but the woman objects, only too late as he already fired an energy blast at Musashi. One a man and the other a woman/mermaid that he witnessed before. As Musashi about to follow Mari, he is knocked down unconscious. The next day, when Musashi and Mari went snorkeling, they discover a portal underwater and at the same time are ambushed by a stingray kaiju. As it starts to rain, Tutomo cowardly hides under the table with Mari mocking him, causing Tutomo to take a nearby soda and spray it on Mari, starting a soda fight with his friend as they are watched again by the mermaid. One of his friends, Tutomo, mocks him for believing in a mermaid but Mari objects it, implied that Musashi might be speaking the truth ever since his first encounter with Cosmos. Musashi attended his childhood friend's wedding and later witnessed a mermaid. Cosmos destroyed the monster, causing a giant explosion and quickly rescuing Musashi from the explosion. As they dueled, Musashi founded that the monster is responsible for turning the Planet Juran into a barren wasteland via it's energy beam.
As it is about to ram Musashi's TECCH Spinnar KS-1, Ultraman Cosmos appeared and saved him. Suddenly, a flying monster burst out from the ground and firing a reddish energy ball. Not only that, Parastan, the planet's protector died. However, much to his horror, the planet appeared to be a reddish and dusty wasteland. Musashi pilots his TECCH Spinnar KS-1 and went on a journey to Planet Juran. It has been a year since Musashi retired from being a Team EYES member and now he is finally pursuing his dream to become an astronaut.