Kizuna takes Yurishia on a date through megafloat Japan. They enjoy a day of seeing the sights, from Tokyo to Kyoto. But then Reiri takes Kizuna aside and tells him a horrifying truth: that if the Hybrid Count of the girls reaches zero, the pilot will die. When Aine wants to push herself to the very limit, and a huge fleet ambushes Ataraxia, how can he stop things from getting out of control?

A huge enemy fleet is bombarding Ataraxia, led by a battleship with a gigantic cannon. Amaterasu does their best to fight them off, but Aine's Hybrid Count is critically low. Kizuna is able to rescue her in the nick of time and take her back to Ataraxia, where he talks with her about her past. He finds out that Aine was also a test subject in Dr. Nayuta's experiments, and that she knows the key to unlocking her lost memories: a more advanced version of the Heart Hybrid called the Climax Hybrid.

Himekawa is guilt-stricken by her failure to protect the citizens as they boarded the Tokyo megafloat. When a mysterious radio signal is picked up by Ataraxia, she leaps at the chance to perhaps finally save a civilian. But when Amaterasu arrives at the source of the signal, they find an enemy from another world, and one deeply connected to Himekawa's past.

Himekawa needs more power to fight against the tri-headed dragon that caused her so much trauma in her past. But the pleasure of the Climax Hybrid goes against the strict and disciplined life that she's forced on herself after she failed to protect the people boarding the Tokyo megafloat. It's up to Kizuna to break down the walls she's built up for herself, and teach her to enjoy the ecstasy she needs to defeat the enemy.

Ataraxia is united with the Masters, the aces of the Western USA megafloat. Despite Yurishia being their former leader, they're very cold to her. Their leader, Scarlet, fights with Yurishia over Kizuna, but their battle is interrupted when another leader from the Batlantis Empire attacks!

After their defeat by Grabel, Amaterasu needs a new weapon to protect Ataraxia: the Connective Hybrid. To use it, Kizuna will have to perform the climax hybrid with two girls at once! He picks Yurishia and Scarlet, hoping to defuse the tension between them. Will the pleasure be enough to cause them to reunite? And can they retake Guam, and eventually Japan, from the Batlantis empire?

The eve of the operation to retake Tokyo coincides with the school festival, and Aine is nowhere to be found! Amaterasu is supposed to be giving a big concert performance at the climax of the festival, so Kizuna sets off in search of her. Can he find her and bring her back in time, or will Sylvia have to go instead?

Kizuna is finally reunited with his mother, who is revealed to be the one who originally sent information on the Eros system to Ataraxia. His mother is working with the Batlantis empire, and is now an enemy of humanity. She tells him to go to Tokyo, where she'll reveal more of her plans. But to break through to occupied Tokyo, Kizuna will need to strengthen his team, which means adding a new member: Sylvia Silkheart. Will young Sylvia be willing to go along with the core install process, and the dangers, and pleasure, that it entails!?

The attack on Tokyo has begun, and Amaterasu finds itself outgunned by the Batlantis royal guards. It's up to the newly powered-up Sylvia to save her the day with her Hybrid Heart. When the defeated enemy general uses her ultimate attack to summon a black hole that can take out Tokyo, she'll have to rely on her forbidden weapon to save the city.

In the climatic battle for Tokyo, Aine attempts to perform a climax hybrid to get the power she needs to defeat the Batlantis royal guard. But doing so means facing memories that may be best forgotten...Can she set aside her fears to gain the power she needs? And should she, if the cost may be the loss of her own identity?