It's all Aqua's faultOK so apparently the demon lord's name is the same as Kazuma's last name. This has been taken to potentially imply some manner of relation. However, if this were true then said demon lord would have had to be sent to Eris's world by Aqua. The character page suggests that Eris is actually an ineffective goddess due to her letting her universe become overrun by a demon lord so evil that he made it so no one wants to reincarnate. But if this utterly evil demon lord was sent there by Aqua, then ultimately she is the one that caused the mess by dumping her "trash" in someone else's yard.
Heaven is as boring as Aqua claims it to beThe behavior of Aqua and Eris seems to indicate she was telling the truth about Heaven. Aqua devotes as much time as she can partying and spent her first nights drinking until she puked (a sign of low tolerance and/or not knowing her limit). She's ever since developed a strong love for alcohol. She also tells Kyouya she's having a lot of fun with Kazuma, despite the poverty and hardships they run across. It's like she wants to have as much fun as she can, before going home. Eris also enjoys spending what little free time she has, pretending to be Chris, and interacting with the new world.
Aqua's banishment was divine usurpation of her officeAqua frequently claims she's a high ranking goddess, which Eris seems to back up. While Aqua doesn't have many followers, their belief in her is significantly greater than normal, meaning she has more power than the number indicates. She had a position overseeing Earth, which is commented on being a first-class world for deities. Even depowered and made mortal, in terms of raw magic might, Aqua is one of the most powerful beings in the new world. Kazuma's selection of Aqua as his cheat item, was the only way the other gods could stop and/or seize Aqua's power. Her banishment is more like the exile of an influential world leader, than some nobody. Incompetent or not, Aqua was a powerful goddess.
Aqua's powers will be nerfed if she leaves Kazuma's party or if he's Killed Off for RealLater volumes confirm that all the "cheat items" granted to the people from Earth that reincarnate in the other world only work to the full extent of their capacities if they are used by their assigned wielders. This is a security measure designed to prevent other people from causing untold harm with them.
Now, given that Aqua is technically Kazuma's cheat item, it'd make sense for the same restriction to be in place. In her case, this probably means that most of her powers will be sealed away for as long as Aqua gets into a situation that qualifies as "don't working for/with Kazuma", such as disbanding the party and going in their separate ways or if he gets Killed Off for Real.
Aqua getting chosen as a cheat item is Just as Planned for the powers of HeavenEven if she is rather flighty, Aqua's magic has proven to be deadly to the minions of the Maou. Heaven has been itching for an excuse to send a deity to directly intervene without breaking the rules. The fact that Kazuma compensates for all of Aqua's weaknesses is not a coincidence, Heaven keeps sending Guile Hero types through in the hope that at least one of them is cunning enough to select the Goddess herself as a cheat item. The fact that its Aqua means that she is a lot more replaceable than the average, actually competent Goddess.
Aqua is seeking attention and worship on purposeRather than feeding her ego, its necessary for her mana regeneration and use of her divine powers. Gods Need Prayer Badly seem to be in effect so Aqua putting her skill points into flashy party tricks is one way to get the admiration necessary to keep her in existence.
Emperor Zell will grow up to be a Feathered DragonEither Zell is an authentic dragon or Aqua's infusion of divine energy will mutate him into one. There are subtle moments when Zell reveals himself to be much smarter than any baby chicken should be, and the feather crest on his head grows more prominent for a mere chick as each volume passes.
Aqua's irresponsible behavior enabled the holocaust and cold war on EarthAqua states when speaking with Eris that she is in charge of Earth, and it appears likely that Aqua has been in charge of Earth's well-being for quite some time. That means Aqua was probably in charge of Earth while Europe while was tearing itself asunder in World War I, while humanity discovered the meaning of true evil in the holocaust, and while all life on Earth was one button press away from permanent nuclear annihilation in the Cold War. Aqua's irresponsible behavior, as seen in the anime and books, would explain the lack of divine intervention on Earth during such times; Aqua certainly would be in character if she were completely negligent regarding the safety of Earth, and would not bat an eyelash if both the United States and the USSR each had a single button capable of destroying all life via absolute nuclear annihilation.
- Bad as Aqua's management of Earth might be, it's in better spiritual condition than the world Eris has overseen. Earth's population has a surplus of souls and a waiting list of souls wanting to reincarnate there, thus being a main source to tap for sending Earthlings to other worlds as heroes. The divine energy Aqua collects from Earth, in whatever guises she takes as Earth's main divine being, ranks her among the top tier deities. Indeed Aqua has followers on worlds OTHER than Earth. Eris cares for and puts more direct attention of the world under her care, but its still a Crapsack World. Aqua also comments that it's illegal for deities to manifest themselves on a planet like Eris does. While Earth has the fear of nuclear annihilation or a global environmental catastrophe, the world Eris manages is constantly trying to avoid genocide of humans, elves, and dwarves from any of the hundreds of Demon Lords that populate it.
- Considering just how often we came to the brink during the Cold War and how we always managed to edge away from nuclear apocalypse, Aqua might have just been far more subtle about things. Aqua is terribly lazy and egotistical but it is the latter quality that ensures that we did not blow ourselves up. Aqua cherishes her worshippers greatly and she would never allow her stewardship of Earth to end with it as a glowing wasteland. The World Wars? We did that to ourselves. However this never threatened the existence of humanity as a whole so Aqua never intervened.
- Aqua is only responsible for young people in Japan, not the entirety of Earth.
Aqua used to be a diligent goddessThe God Realm seems to run on a system of meritocracy. It's odd that Aqua would have been given supervision of a premium world like Earth, without first going through the same training and low level planet administration as Eris. In fact, she could have trained on the same world as Eris, given her clergy were already established and highly loyal. Aqua shows signs of excellent work ethic during her part time jobs, and she has encyclopedia knowledge of the God Realm rules. At some point in her divine career, most likely after gaining jurisdiction over Earth, Aqua just gave up caring about her duties and became the lazy, detached goddess Kazuma encounters. This troper's best theory? Boredom.
Aqua controls water in all three statesAqua has the power to use water in it's solid and gas forms, but avoids manipulating it in those states for making her too cold and too hot.
The "pants" Darkness wore in S2E08.They are actually opaque pantyhose.
The Ruffian is the Demon LordAs Mother's Basement talked about in his analysis on the second OP, the Ruffian could very well be the Demon Lord in secret. For those who don't know the Ruffian is the guy with the Mohawk who hangs around the bar and usually cheers Kazuma on. The reason he cheers Kazuma on is that him and his party defeated Beldia and Valir successfully and he is actually looking forward to finally coming face to face with him once he defeats the other generals. In fact one instance where he cheered Kazuma on was a monologue after Valir's defeat.
Explosion is a modified Dragon SlaveWhether it's because Lina herself showed up due to a magical artifact mis-hap or one of the people Aqua sent over to the world was a huge Slayers fan, the end result was the same. No Shabranigdo to draw power on caused the end result to be quite different than intended.
Megumin's butt tattoo serves the same function as a Driver's License or Social Security Card in our world.In Volume 3, Kazuma notices that Megumin has what looks like a tattoo on her butt, but dismisses it. Megumin later confirms that all Crimson Demons have tattoos on their bodies and in different places, in the Megumin spin-off novels Megumin reveals that her tattoo is a series of numbers. This is necessary due to the fact that Crimson Demons all look alike due to having their DNA modified in the distant past and if one of them dies on an adventure, the clan needs a way to quickly identify the body.
Darkness is aware that she freaks everyone outAnd she purposefully goes on her masochistic rants in front of her enemies to Break Them by Talking. While this may her simply being her the first several times it happens, her Character Development in the more recent novels seems to imply that she's less obsessive about seeking out abuse (though willing to accept it if it does happen) and more willing to help out when her party needs it.
The Demon King is Kazuma's brotherIn Volume 5, we learn that Kazuma has a little brother (one that Kazuma tricked by paying the girl next door to give him Valentine Day chocolate and that way winning some sort of competition he had going with his younger brother). If time shenanigans are in effect and his brother dies after Kazumas death but arrives before him, then it could work, especially if being a scumbag is a family trait.
Megumin is related to Mr. Torgue.Because explosions. She's also drinking buddies with Tiny Tina.