This ends up to be a LONG summary, it’s full of tl;dr but feel free to read. It feels more like a translation instead. I didn’t like Cain at first, but after finishing his route he became my favorite.
Cain first introduced himself as a foreign student who doesn’t fully understand Japanese. Futaba got into trouble with some guys when looking for her mother in the city, and Cain was the one who saved her. Being a stereotypical gaijin, Cain is very bold. He flirts with Futaba on numerous ocassions, using his bad Japanese as an excuse when she gets angry.
The flirtatious gaijin is only a disguise though. It was soon revealed that he is actually a member of NEDE, and an executive on top of that. His job is to give punishment to those who tries to defy or escape from NEDE. Cabracan and him attacked Futaba’s school later, which eventually resulted in her and the twins getting kicked out of school.
Futaba was really shocked when she found out about his identity, moreover since Cain said that she’s such a stupid girl to be deceived by him. However, Futaba still tried to contact him after that. He then told her that he had a present for her and asked her to come to the shopping district the next day. Futaba wasn’t sure if it was really okay to meet Cain again, but decided to come anyway since he offered information about her mother.
The ‘present’ turned out to be a NEDE pass card. Since they were enemies, Futaba was surprised and asked why did he give her such an important thing. Before Cain could answer though, they were interrupted by Reimei and Shirou who had been following her ever since she left the mansion. Cain escaped and Reimei told Futaba not to trust that guy anymore.
When they examined it later, the pass card he gave her was genuine. Since Cain has deceived Futaba before, Reimei thought that the pass card is a trap. He also started guarding and watching Futaba after that, just in case Cain tries to contact her again.
Cain called her again that night, and answered her question from earlier: he lost his reason for working with NEDE. He didn’t want to spill the details though, and they were soon interrupted by Reimei again who confiscated Futaba’s cell phone.
That night, Freikorps’ mansion was attacked. Right after Reimei told Futaba to stay in her room, Cain broke the window and came to pick her up.
Futaba didn’t know if she should take his hand or call Reimei instead. But after Cain said that they will rescue her mother, Futaba decided to go with him. Before escaping, Cain told the twins that he’s not working with NEDE anymore. He just used NEDE’s troops who were attacking the mansion because it’d be easier for him to reach Futaba.
The next morning, Futaba woke up in a car dump with Cain lying next to her. After some teasing and apology, Futaba asked Cain to explain his reasons for helping her. At first he refused since it’s got nothing to do with her, but eventually gave up after Futaba said that she wanted to know more about him and his conditions.
Cain’s younger brother had a weak body, but he was a hanki with a strong blood, close to those of a pure one. NEDE was interested in him because of his blood, since having a strong blood means that he would be able to endure a strong bugai. Cain knew really well that NEDE will use his brother in various experiments, so he made a deal with the organization.
In order to keep his brother away from being used in experiments, Cain would do anything NEDE ordered him to do. However, when Cain didn’t know it, they eventually tattooed a strong bugai to his brother’s body. A normal hanki wouldn’t be able to endure that, and Cain’s brother lost his life as the result.
The researchers already knew what would happen, yet still carried on with the experiment. To Cain, they were only toying with his brother’s life. He wanted to help rescuing Futaba’s mother in order to get back at them.
Futaba then decided that she will trust Cain. It’s true that he has deceived her before, but she doesn’t think that he’s lying now. Cain said that Futaba must be the easiest person to deceive since she will continue to trust, but he was happy with her decision.
When the night came, Cain and Futaba infiltrated NEDE’s base. After taking care of the guards outside and borrowing one of the uniforms for Futaba, they found that the soldiers inside had been brutally murdered. Among them was the wounded Harphas lying on the floor. Before he died, he told them that someone betrayed the boss and directed them to the underground chamber.
In front of the elevator, they met a hooded boy in bandages who turns out to be Cain’s younger brother — Abel. Cain was happy to see him alive, yet Abel didn’t recognize him at all. He was ordered to guard the elevator, and started attacking Cain with various skills ranging from Harphas’ poison gas to Cabracan’s attacks. It wasn’t long until he summoned his bugai, a shield and a strange creature known as armor eater.
Cain tried to fight back, but his whip was soon eaten by the armor eater. Abel then asked him to leave, yet Cain refused to do so until he knows what NEDE did to Abel. He was ready to attack Cain again when suddenly an explosion was heard fom the underground chamber. Abel quickly took the elevator down, with Cain and Futaba following him soon after.
Right after they reached the underground chamber, something started to burn and the room was soon on fire. They saw Futaba’s mother there, along with Abel and Ensof. Realizing that it was Ensof who betrayed NEDE’s boss, Futaba asked him if he was the one who did all of this to her mother.
Here, Ensof mentioned the first hint about Futaba’s mother. He was wondering why Celaeno, a female DEHAB, was unable to endure the bugai. He found the answer when Futaba appeared asking about her mother. Apparently the female DEHABs, called Harpies, would lose all of their power upon giving birth to a child. It was possible that Futaba inherited Celaeno’s power, since she is her daughter.
Of course Futaba didn’t understand anything about Celaeno or Harpies, and so she didn’t know the meaning behind Ensof’s maniacal expression as well. The chamber started crumbling soon. Cain took Futaba out despite her attempts to get to her mother. Ensof chased them saying that he won’t let Futaba escape, and that he will insert a key bugai into her. They got into the elevator just before Ensof got his hands on her.
Cain escaped from NEDE’s base while carrying Futaba, who was crying because they failed to rescue her mother after all. After what happened with Ensof in the underground chamber, it seems like Futaba would be their next target. Cain then took Futaba to the safest place in the city, Freikorps’ mansion.
The twins welcomed Cain with a hostile attitude, but then agreed to hear what they had to say upon Futaba’s plead. He was planning to go back and face Abel after explaining the situation, but Shirou asked him to stay because it’d make Futaba sad if he died. Since Cain’s bugai was eaten, he agreed to stay until it recovers.
Days passed with Futaba having nightmares about her mother in the burning underground chamber. Their failure in saving her was haunting Futaba, and she was desperately looking for a way to save her mother. She woke up to find Cain in her room one night. Seeing Futaba looking so down, Cain asked her if she had lost her reason for fighting.
Taking Futaba’s silence as an answer, Cain said that he won’t tell her to get back on her feet after losing someone important. But he still had his reason to continue fighting, as he wanted to return Abel to normal. That’s why he’s bidding farewell to Futaba because he can’t stop fighting yet.
Futaba then asked what if Abel won’t be able to return to normal. To that, Cain answered that he will definitely stop him. Even if that means killing Abel. He didn’t want Abel to get his hands dirty even more than now. Realizing that Cain was planning to have a death match with Abel, Futaba asked him to take her along.
However, Cain refused to let her come. He was only using her to get back at NEDE, and he wouldn’t mind taking her along before. But now he didn’t want to put her in danger, and that feeling outweighed everything else. He wants her to live.
Gently stroking Futaba’s hair, Cain admitted his feelings. He only thought of Futaba as a stupid girl who trusts people too much before, but then he started to love her. He never cared about anyone except Abel before, and now that he came to love her, he didn’t want her to get involved in battle anymore.
Cain thought it’d be better for both of them if he leaves before his love for her grows stronger than that. He then asked Futaba not to forget him and left.
Realizing that she also shares the same feelings with Cain, Futaba chased after him. She asked him to take her along, since she wants to stay by his side. Cain noticed that Futaba feels the same, and asked her wouldn’t it be better to part before they come to love each other more. Futaba answered that she wants to love him more, and wanted to stay with him until the end.
After hearing Futaba’s feelings, Cain hugged her and said that he was happy. He agreed to take her along.
The next day, Futaba and Cain went to see the master in his shop. Futaba asked him to insert a bugai into her, since she wanted to fight alongside Cain. At first both Cain and the master opposed the idea because of the high risk, but eventually agreed to let Futaba get her own bugai. The master also told them that there might be a chance for Abel to return to normal if they could beat his armor eater.
Futaba spent the next days training to use her new bugai, with Cain helping her so that she can use it properly.
One night, Reimei was attacked by someone in NEDE. It was an unexpected attack, and Reimei noted that the attacker was a hooded young boy covered in bandages. Lately the members of Freikorps were also attacked by the same person. Though they didn’t know why Ensof ordered Abel to do that, Cain knew that it was time for him to stop Abel.
When they arrived at NEDE’s base, Abel and Ensof were waiting for them in front of the gate. Ensof knew that if he ordered Abel to attack people in order to copy their attacks, Cain will definitely come to stop his brother. And by doing so, Futaba will also come.
Cain was ready to face both of them when suddenly the twins showed up. They saw Futaba leaving the mansion and followed her. The twins then chased after Ensof, leaving Abel for Cain and Futaba to take care of. Cain asked Futaba to take care of the armor eater, since it’d over if his whip is eaten again.
During the fight, Futaba kept hearing some noises. She noticed that the voice she heard was begging her to kill him. Upon attacking the armor eater, Futaba noticed that the noises were actually coming from Abel. The more he fought Cain, the more Futaba heard the noises. She soon realized that it was the way Ensof used to order Abel, suppressing Abel’s own will and directing him towards negative emotions.
When the sun rose, Futaba spotted the armor eater appearing from the shadows. Using her bugai, Futaba shot the creature, killing it. At the same time, Abel let out a scream and collapsed to the ground. The twins soon came back and reported that they had taken care of Ensof as well. They went back together to the mansion with the unconscious Abel. Cain thanked Futaba for all the things she did and said to him.
After they got back to the mansion, Cain spent his days nursing Abel. Futaba met him in the hallway and reminded him to eat and rest properly. Cain said that he knew he had chosen the right path because she stays with him, and he will tell her what he really feels when Abel wakes up.
Futaba went to the garden for a walk afterwards. Soon, Cain came looking for her because Abel has opened his eyes. Cain then kissed her, saying that he can’t be without her. Previously he said that he was starting to love her, and currently he’s already in love with her. Futaba answered that she will always stay by his side.
Instead of saving Abel by defeating the armor eater, Futaba decided to fulfill Abel’s wish by killing him instead. Dying in Cain’s arms, Abel returned to his normal self.
He didn’t know what has happened up until now, and only thought of it as a long dream. Abel asked if he caused more trouble for Cain, and said that if only he’s not around things would be easier for Cain. Cain then told Abel to sleep since he must be tired. Abel died after saying goodbye to his big brother.
When the twins returned, Cain asked Futaba to go back first since he still wanted to stay with Abel. Futaba apologized, but Cain only thanked her since she did the thing he couldn’t possibly do. When he said goodbye, Futaba knew that she won’t ever see him again.