This is like a part 2 of the whole angst Kaga's backstory idea I had for him. Here's part one :D
Let me explain in more detail in this idea of angst backstory ->
I've decided to make Kaga be born in a very intelligent family instead of making him a gifted child (the idea can work still, but for now, I'll keep it this way). Kaga is a genius just like his parents. Throughout the years of his ancestors and way before he was born, they had made excellent discoveries in science and technology that were a huge help during their time. Each generation did something new, something better than the previous one.
Because of this, this was turned into a very toxic tradition to each future generation to prove themselves of their intelligent, skills, and are worth the pride of the family. Each Kusha member made it their goal to do or discover something better than the previous one to show that they were worth the pride and spot of being in the family.
This continued. Eventually, Kusha's parents had to face it as well to prove themselves to be part of the family (mostly Kaga's mother who got married into the family. She had to prove herself as well). One of the biggest achievements they have ever made was being hired by Saikou Corp.
Saikou Corp is already hard enough to be hired by from how strict and limited the rules are for finding the perfect employee.
With that, they were able to prove themselves to the family. Now, they have the tools to discover new things in technology and show it off even if it will be under the name of Saikou.
Then Kaga was born. He was expected to become someone much more successful than his own parents and, overall, be someone who is worth being in the family. During his childhood, he was around adults and rarely around children his age.
He had to take many classes to improve his skills and IQ and learn how to work with his own hands at a very young age. There were times when Kaga did get a break from everything, but Kaga realized that breaks were a waste of time, so he rarely took breaks and continued with his education.
Once he started building things, that's when his obsession of showing his family that he was worth the family name and pride developed. He started building the most unique (and dangerous) gadgets. He entered many science competitions to show off his unique gadgets and show off his talent and intelligence to the children who entered.
This caused him to have a lot of problems with other children his age. The children were mostly jealous of him, which caused his gadgets to be sabotaged so he wouldn't win (again). That was when the whole thing was where Kaga would build his own gadget to scare the brats away and to stop messing with him and his hard work. That was probably the only times when he felt like an actual kid.
As the years continued, Kaga's obsession of winning his family's pride become much more toxic.
This took place around his early teens. For the first time, Kaga was face to face with one and only Saisho Saikou (Before this, he did see Megami a few times before since his parents do work in Saikou Corp).
Saisho Saikou was known as the most successful and powerful man of the 20th century. An amazing inventor who founded Saikou Corp and created the most used devices in Japan. He was also the CEO of Saikou Corp.
There was a conversation between these two that drove Kaga into getting the idea of world domination. World domination was something that Saisho Saikou wanted. His idea was destroying it, which Kaga didn't know during the time.
Something snapped in Kaga. If he wanted to show his family that he was worth being in the family, the last name and their pride, why not aim to something that none of them have ever tried before:
Taking over the world. Forming the world the way it should be from the start, but for this, he had to somehow be part of the Saikou family or at least aim towards becoming CEO himself.
That was his goal: to become CEO and take over the world and clean it up.
For the rest of his years, he continued building gadgets but added experiments months after his talk with Saisho. He made it his goal to not only prove himself to his family but to be able to get the attention of the Saikou family. To do this, he was willing to go to the extreme to accomplish his goals.
Now that he was in Akademi and officially an adult, he was able to use himself as a test subject without having his own parents getting in the way. The grey-white hair was a result of his experiment that he decided to do on himself (and the rest of the science club). With the experiments he had made and planned, he would use himself as a test subject.
Kaga was sure that he wasn't going to most likely survive some of his experiments, but at this point, he didn't really care as long as he was able to prove to his family and get the attention he wanted from the Saikou family, even there was a chance of him dying. He was willing to try.
There were times when he was sent to the ER to get help after an experiment went wrong.
Even after the traumazing near death experiences, he continued.
The toxic tradition of his family turned him into a mad scientist that he is now.
Kaga is slowly destroying himself over this toxic acceptance of his own family bloodline that was created while Megami is slowly destroying herself as well over the toxic expectations of being "perfect" and the "perfect" CEO for Saikou Corp that was created by her own grandfather.
I don't see Kaga as the type of expressing his emotions towards the whole toxic tradition because he was alone. No one really was there for him during his childhood. He didn't have anyone to talk about his feelings on the subject. He pretty much pushed his feelings to the side and never knowledged them.
Same thing with Megami. These two remained doing what they needed to do to prove themselves to their families.
That's until Ayano decides to matchmake them, or the two start talking to each other. Once they find out what they went through, they realize that they're not alone. Even if it's for different reasons, they knew the feeling of wanting to prove themselves to their families.
I feel like at least they would use their angst backstories against each other at first. For example, Kaga would say along the lines of:
"Are you willing to sacrifice the function of being a human being to prove to your father that you're the perfect Saikou and perfect future CEO for Saikou Corp?"
Then Megami would say back:
"Are you willing to sacrifice your life to prove that you belong in your own family and you're worth their pride? Is it really worth it?"
Kaga would think of the question along with Megami. Knowing how they are, they would be too stubborn to stop what they're doing now.
However, a question behind their minds would repeat in their heads:
"Is it worth it?"
With time, they realize that, that everything they are doing is not worth it.
One is destroying himself to near death while the other is slowly losing the function of being a human being. Megami was turning into a robotic individual just like her father.
A robotic creature that isn't seen as a human being at first to her own family. Megami was a toy/object that was being formed into someone her father wanted her to be.
These two come together again and accept that what they're doing is not worth it. Then Megami would say:
"You and I are the same, Kusha-san. Even with the different circumstances, you and I suffer in the hands of our own families. I didn't want to accept it at first, but it's time that I fight for what I wanted and needed. It won't be easy, unfortunately."
Then Kaga would say back along the lines of:
"Who said it was going to be easy? Facing the expectations of our own families and not following it will be the hardest part for them to accept. Fortunately, you're not so alone anymore, Saikou-san. You have me now. It's going to be you and I against the world!"
Megami would say something that would discourage Kaga on what he said so Kaga wouldn't get too loud, but deep down, she was happy to have someone to relate to in a very deep and emotional way.
:]