Now, even though he is severely blunt about his immaturity, he is also quite insecure and touchy about certain things. From time to time you may even catch him in a sour mood and he may or may not snap at you. This is quite rare, however, as he tries his best to put on a grin in these situations. He can also be quite clingy when it comes to people he ends up caring a great deal about, especially if he becomes insecure about friendships and relationships. No matter what, he'll always bounce right back to the mischievous, fun loving goofball he really is, so take care not to take it too harshly, whatever he does.
=> Katsuo and his brother had a busy childhood. They didn't make friends easily, and those that they did make didn't generally stick around for very long. Most of the time it was just the two of them, and they were okay with that. At home, they had a nanny who looked after them when their parents were busy or at work. Sometimes they felt bad for taking advantage of how nice she was to play pranks on her, but most of the time she took it all in good spirit.
They were trouble-makers in elementary school, dominating the playground and causing havoc for their teachers. Even at such a young stage they frequently talked back or skipped classes. Sometimes Katsuo figured the teachers liked when they skipped classes more than when they attended them, because whenever they were in class something always seemed to happen. One time a bee got in the classroom, another time a girl got gum stuck in her hair, yet another time the sprinkler system malfunctioned and the classroom flooded. Usually he and Kazuo had something to do with those catastrophes, except for the flooding part. They actually had nothing to do with that, not being old enough yet to know how to break a sprinkler system.
A lot of the time at recess, none of the other kids would want to play with them. It wasn't necessarily that they were bullies, but they didn't play games they weren't good at and the games that they did play they were way better than the other students at. Not to mention a lot of kids were just freaked out by the way they would talk in sync with each other and looked so much alike. Sometimes when no one else would play with them, he and Kazuo would play tether-ball by themselves. Most of the time he won, but sometimes he let his brother win.
Of course, all their bad behaviour took it's toll and they ended up being kicked out of that school sometime in fourth grade. Katsuo could still remember how mad their parents were about it, and how much he and his twin absolutely dreaded the school they were placed into next. It was a private academy and they had to wear super tacky uniforms. He hated them. Kazuo hated them, too. It only took a week before they found themselves barricading in their room to remodel the clothing into something they liked more. At this school they made more friends, but none of them were ever as close as they were to each other. They ended up dabbling around in sports, and found out soccer was a new passion. It wasn't really surprising they picked up more activities though, since they'd been active in their elementary years.
By middle school they had also taken up the hobby of playing tennis with each other in their free time, which often became very competitive and they would spout out insults to make the other mess up. It was usually all fun and games, but sometimes he would say something that would actually hurt Kazuo and he would feel bad. Whenever they had friends or anyone around at those times, he and his twin would play up their taboo show that they had been practicing. Of course, it was entirely fictional, and neither of them saw each other in the light of a lover. All their friends were always really intrigued by it though, even if some of them acted disgusted, so neither of the twins ever told the secret that they weren't really together like that. Not unless it was to someone they had developed an interest in dating, and that didn't happen until around high school anyway.
In high school the twins took marching band, because the school no longer offered soccer as a course. In the end, they dropped out of the class. While they did enjoy it, it just wasn't the same, and they had too much pent up energy from sports. During those last few years in school, he and his brother took turns trying to open up to others. Only to discover that no one even tried to understand them very well, and for their senior year they were back to only being friends with each other, ignoring the rest of the student body.
Since graduating, they've continued to stay by each other's side, hating to be separated for anything. They still did everything together, and basically assumed they would until they grew old and died together.
=> "Frisk allows the Pokémon to see the opponent's held item upon entering battle."