To get an idea of what Kosaku is like, imagine a guy who is insane. Imagine that this guy is so messed up in the head that he would kill anything in sight to get his way. Imagine that this guy would destroy the universe if he would gain something by doing so. Kosaku is that guy.
Kosaku was very different in his first twenty-three years compared to the rest of his life. He was born to Samuel of the Arlian tribe occupying the northernmost end of the Great Cave Offensive. For years afterward, Kosaku became increasingly and increasingly jealous of his brother as it became more and more apparent that he would never be able to use magic like Ippei could. Kosaku absolutely could not stand Ippei's patronizing attitude, and so, when at the age of 19 Ippei joined the Galaxy Soldier Army, Kosaku decided that he would, at all costs, outdo Ippei.
In three years, Kosaku succeeded. At the age of 22, he had reached the rank of General of the Melee Weaponry Branch of the GSA before Ippei could become the General of the Magic-Channeling Weaponry Branch. Kosaku was satisfied with this for a short while, but it didn't last for long.
A year later, Kosaku was surprised by the then-current Reincarnation of the Sun (with the Element of Fire), Urgis Emanus. Urgis explained as quickly as possible that his million year lifetime was almost up and that he had selected Kosaku to be his successor. Obviously, Urgis did not have time to do research and as such chose Kosaku because he assumed someone who was that high of a rank in the military must have been disciplined, trustworthy, and noble.
Kosaku was ecstatic. One more thing he had over his brother. Then Urgis informed him that he had been told by the Reincarnation of the Moon who the new Reincarnation of the Moon would be: Ippei.
The second Kosaku received the powers of electricity was the second he irreversibly disabled Ippei's higher brain functions.
Kosaku then went mad with power and began his attack on the entirety of Dreamland, starting to form the nation of Kosakuland. But he greatly underestimated the strength of Dreamland, and even he could not fight them off. He fled to space with a Keke Space Station that was recently constructed, causing almost all of the Kekes' resources and years of work to be a complete waste. It would take them nearly two hundred thousand years to build a new one.
While Kosaku was away from Pop Star, he controlled Ippei from space using his powers of manipulating electricity. During the time that Kosaku was away, many events happened, such as Ippei being cursed by the Book of Knowledge, an all-out war between the Batamon and Wehhanians, and Ippei unleashing the power of Dark Matter upon the planet of Wehhania, effectively wiping out most of the planet's population.
The Great Cave Offensive: Revisited Edit
Kosaku spent more than two hundred thousand years in space. He was bored. He was so ridiculously bored and the air was so ridiculously stale and the whole place was falling apart. Kosaku wondered why he bothered living. He thought for about three months about what he was forgetting before he remembered what was even going on. He was... something to do with the sun. And electricity, or something. Then he got some mail from Exuro, who wanted him to go to the Great Cave Offensive for an expedition. Of course, this was a horrible, horrible choice for Exuro to make. Kosaku had no idea where he was or what direction Pop Star was and this was probably the sole reason he hadn't taken over the world and killed millions of people. Exuro's mail, however, conveniently included the coordinates of Pop Star.
In about twenty-four minutes Kosaku had warped his way there.
The thing was, however, that Kosaku was not really that violent at the time. What Kosaku hadn't realized was that Ippei's curse (which Kosaku's mind had since gone into denial about) and the demon inhabiting Ippei affected Kosaku's sanity as well. Kosaku's increasing dislike for Nathan also fueled this violence. A few days later, after Kosaku had regrouped with Ippei, Kosaku completely lost it and began to reform Kosakuland.
Then Kindra killed him. Fun times.