In Hong Kong, two men tell Gaulon that they can’t trust him anymore because he left the cargo behind in Helmajistan. Gaulon smirks and shoots them both, remarking that he can’t do his part-time job because of Sousuke. He pulls out a disk labeled ‘Toy Box’ from his coat pocket. At school, Chidori asks Sousuke why he had a security gate built at the entrance. Sousuke replies that it’s for the culture festival, with the theme being security. Should the culture festival be attacked by terrorists, the gate can hold them off. Chidori asks the students why they didn’t find this suspicious, and Shinji says that they actually agreed with Sousuke’s idea. Chidori tells them that the gate alone cost them nearly the entire festival’s budget and Sousuke says that they can still get an armored vehicle for cheap, getting hit over the head by Chidori. Chidori demands the gate be demolished but accidentally walks into the gate’s security beam and gets sprayed with red paint. She shoves Sousuke to the ground and yells that she’s wasting her youth on a military nut when she should be making great summer memories. She tells Sousuke that she’ll just spend the remaining week doing nothing. Sousuke asks if this means she has spare time, and when she confirms it he asks her to accompany him to the southern islands. Blushing, Chidori asks if he’s serious. Sousuke replies that he is and that he was thinking of it for a while. Kyoko approaches wanting to talk to Chidori but Shinji tells her to be quiet so as not to kill the mood. After confirming that they won’t be doing anything strange or dangerous, Chidori accepts and accidentally walks into the gate’s beam again. Despite being sprayed with blue paint, she’s not angry and says the color goes well with summer. At home, Chidori tries out a white bikini she burrowed from Mizuki and wonders if it’s too daring. As a precaution, she packs her school swimsuit anyway, along with a camera that Kyoko gave her. Meanwhile, the crew of the American submarine Pasadena spots the Tuatha de Danaan on sonar and thinks it’s going to ram them. Bracing for impact, they notice that it has harmlessly passed and dropped out of detection. XO Takenaka tells captain Saylor that it might have been the Toy Box from past wars, a ghost submarine. Saylor remarks that the spirit of the Toy Box’s captain is that of a psycho and vows revenge. Tessa regrets using the Pasadena for practice and Mardukas says that wounding the crew’s ego was a risk they had to take in getting results for this test run. Tessa says they should return to base before they miss the birthday celebration since they have a guest coming tomorrow. Chidori is amazed that Sousuke has prepared a private jet to transport them. As they’re boarding, Sousuke lets it slip that they’re going to Mithril’s West Pacific base to meet Tessa, causing Chidori to stop in her tracks. Tessa receives a message stating that a chemical weapons factory on the Ferio islands has been taken over by armed terrorists and orders the Tuatha de Danaan to change course and head there. She says that it would be disastrous if the factory blew up and Mardukas remarks that the United States will probably dispatch arm slave squads. Tessa wishes the situation could be resolved that easily. On the plane, Chidori is being very cold to Sousuke and the latter receives a transmission from Weber telling him of the change in plans. Weber tells him to rendezvous with the Tuatha de Danaan as soon as possible and bring along Chidori as well by orders from Tessa, since the sub is about the safest place she can be right now. Sousuke asks Chidori if she has a swimsuit and tells her to change into it quickly. Sousuke quickly puts a life jacket on Chidori and leads her to the door. Chidori discovers to her horror that they’re going to jump out of the plane. When they splash down, the Tuatha de Danaan’s sonar operator notes that they’re struggling in the water and patches the sound through. Tessa hears Chidori yelling at Sousuke and says it’s alright for them to be left alone.
Sousuke and Chidori ride the Turtle to the Tuatha de Danaan. Inside, Tessa apologizes for the inconvenience and orders Sousuke to inform the crew of their arrival. Tessa offers Chidori a change of clothes and a tour of the sub. Tessa leads Chidori to the hangar where Mardukas thanks her for her courageous actions and the entire crew salutes her. Embarrassed, Chidori salutes back and Tessa says they invited her here to celebrate the Tuatha de Danaan’s first birthday. The party starts with a game of bingo where Weber announces that the winner will receive a kiss from Tessa despite the latter’s objections. Sousuke, Gail McAllen and Lian Sahopin are close to winning. Tessa and Chidori have conflicting wishes about Sousuke winning, but in the end Gail wins. On the Ferio islands, the American M6s are getting slaughtered by Gaulon’s new Venom arm slave. While Chidori and Tessa sing karaoke, Weber remarks that Chidori is beautiful and Sousuke says he isn’t interested. Sousuke thinks that they shouldn’t be singing and dancing while the Tuatha de Danaan is under operation, and Weber says that despite being experienced soldiers they still need to relieve their tension. Gaulon’s squad of Shadows secure the perimeter and one of his men informs him that Mithril will be coming soon and that both of ‘them’ are on the Tuatha de Danaan. He reminds Gaulon that no harm should come to them, and Gaulon assures him of that though he remarks that accidents can happen.
We’re approaching the final stretch. The Tuatha de Danaan’s crew has a party to unwind before setting off to what appears to be a fierce battle. Gaulon now sports a new head scar and a new arm slave with the scary ability to make cockpits explode, but there’s no point in complaining about that anymore. Chidori’s gone back to being a bit more tolerant with Sousuke than before, and it’s obvious by now that she likes him and trusts him enough to travel alone with him. Suddenly naming two crew members surely isn’t coincidental, and that means something unfortunate will happen to those two.