Dean listens to his student, and his explanation. It wasn't that bad, but there was much more that he could add to it.
"I call everyone kid, kid >_>."
Dean says, annoyed at this guy's insolence. Who did he think he was? A mere seer before the mighty power of a Black Knight.
"Anyway, on to your explanation. The foul chakra of the Juubi remained behind after it had been sent to the moon, sentient and living, looking for its first host. This first host was Anshoku, a bitter man. As it entered his body, it burned the symbol of the Demon onto him. The foul chakra, in an attempt to merge with the Juubi once more, traversed to the moon, the dark side of the moon. Nekura have the uncanny ability, of opening a portal between the moon and earth in order to control the Keigoku and use it in battle.
Now, as you know, the Nekura "summon" and "control" Keigoku by opening portals between the Earth and the dark side of the moon. These portals I speak, are opened in free form, and can be done anywhere on the battlefield but only Keigoku can traverse through said portals. So, releasing Keigoku from a portal would count as a technique, but opening a portal can be done in free form. Opening the portals are silent as well. We each have a Mark of the Demon, which acts like a seal which connects our chakra to the Juubi's chakra (Keigoku) on the moon. The Mark of the Demon allows us to create portals, and draw the chakra (Keigoku) through the portals.
As you stated, Keigoku has the ability of harming those it touches due to its corrupted nature. It can cause searing pain to the minds of those not part of the clan. Longer exposure to Keigoku can cause complete shattering of their minds, and even a vegetative state. Keigoku is also capable of passing through physical substances without minds (depending on clan rank, it can through more stuff, the higher you are in the clan). The Keigoku has an ability that when it touches a summoning, it completely turns them against their summoners.
Higher ranking Nekura members even get the ability to use Keigoku that had struck the opponent, and bring it back into themselves and firm their minds in order to ignore any pain the received. Though that ability is only for Black Knight and above (still have to learn this myself >_>). Another cool thing that we have, is that the foul Keigoku we control, make Bijuu believe that we are one of "them" since its almost the same chakra that Bijuu are made of. This means that Bijuu will always refuse to attack a Nekura, not matter what state they are in. However, this also brings us to the effects the Keigoku have on us.
Due to being fouled by Keigoku, Nekura automatically reject foreign chakra from entering their bodies. This makes Medical Ninjutsu more difficult to perform, making it three times harder to heal a Nekura and Genjutsu (placing foreign chakra in someone's mind and chakra flow) and Gentle Fist (striking the opponent with pure chakra, and inject chakra through their fists into the opponent's chakra flow to affect them) can't harm a Nekura because of said ability."
After having spoken for a while, Dean scratches his head and looks at his student.
"Uh, any questions? No matter how simple, feel free to ask them now."