“-suke” is a common ending for male names (human and sometimes pets). “Chomu” is the weird sounding bit typical of Crimson Demon names, and doesn’t (necessarily?) mean anything itself.
Apparently Chomusuke being female wasn’t revealed in the LNs until much later on, but I don’t think it much matters beyond the “what, I thought she was male this whole time!” joke from the -suke part of the name. Don’t quote me on this though.
The word translated as “children” here is “o-ko-sama.” The usual word for “child/children” is kodomo, which is what Megumin uses when saying “don’t treat me like a kid!” or whatever. O-ko-sama adds the “honorable ‘o’” prefix and the -sama suffix to the base word “ko” to make an especially polite way of referring to other people’s children; one of the most common situations you’ll see it is on restaurant menus, where it’s the word used instead of “kid” in “kid’s menu” or “kid’s meal.”
It’s also used sarcastically, like here, to refer to someone with a young/innocent/naive view of whatever. In media especially it’s common when poking fun at young characters who hate being treated like a kid.
The “honorable ‘o’” (which can also be ‘go’, it depends on the word you’re attaching it to) is something you stick onto words to kick up the politeness level and/or when speaking in ‘feminine’ language (Japanese is a very gendered language in terms of ‘men talk like this’ and ‘women talk like this’). However, it too is also sometimes used sarcastically or jokingly, or to soften the tone of something. For example “obaka” is kind of like a cuter way of calling somebody a baka (not to be confused with “oobaka,” which means like big idiot).
One of the most common words for “balls” (like, those balls, yes) in Japanese is “kintama,” which translates literally to “gold ball(s)”. So yeah this is a much more obvious balls joke than you might expect.
The phrase she uses here is “charm point,” which is a Japan-original phrase using English words. It’s used to describe specific bits of something that are particularly cute/appealing, either naturally or by design. In this case she’s referring to that hair loop of hers. If you asked a…less scrupulous Japanese Konosuba fan what Aqua’s “charm point” is, they’d probably bring up the “is apparently going commando” thing. A more wholesome example would be Pikachu’s tail and how it’s shaped like a little lightning bolt.
The “Aqua is apparently going commando” is also a reference to a Japanese meme, “haitenai” (lit. “not wearing [panties]”), referring to when characters would be drawn in ways where it looked like they weren’t wearing underwear but you couldn’t tell for sure.
This is a reference to a real-world scam that has plagued Japan for decades. Basically someone will call up random phone numbers, saying “It’s me, it’s me!” and hoping whoever answered the phone will be like “oh it’s my son, what’s wrong?” From there they convince the (usually quite elderly) target that the caller, posing as their child, has gotten in trouble somehow (lost a briefcase of cash for work, etc.) and urgently needs to borrow some money. It’s very easy to do account-to-account bank transfers in the Japanese banking system, so they can just give the old person a few details over the phone and have them send money that way.
That may sound kind of absurd, but it’s been a relatively big problem for a long time; there are still police-run awareness campaigns about it even today, and when sending money through an ATM (the most common method), there’s a warning message you have to go through about this and similar scams.
“Yunyun” sounds strikingly similarly to “tayun tayun,” a common sound effect for…bouncing/swaying breasts. (It’s not a coincidence, no.)
This is a Japanese meme, “ku-koro.” It’s short for “Ku, korose!” which (in context) basically means “Urgh, just kill me!” The original context is that it’s the stereotypical thing for proud female knight characters to say when captured by orcs and about to be subject to certain heinous deeds. Though it started as a porn thing, it’s gotten more mainstream exposure as a gag line in stuff like Konosuba (seen here), Puzzles and Dragons, and various other (non-porn) fantasy series.
There’s a NicoDictionary entry for the phrase that lists it as first gaining steam after trending on Twitter in early 2013.
He uses the phrase “oyakusoku” here, which is a specific technique that is popular in Japanese comedy. It’s the word for “promise (yakusoku)” plus the same “honorable ‘o’” mentioned above. It basically is the same concept as a running gag, except on a much larger scale; instead of being a gag that runs throughout an episode or series, it runs through entire genres or even across multiple genres.
It generally takes the form of “in X situation, Y happens.” One of the most infamous of them in anime is the “guy walks into a room→girl is in the middle of changing clothes in the room→ girl inflicts violence on the guy.”
In a lot of ways it is similar to “cliché” in English, except it’s a bit broader in scope and doesn’t have the negative connotation that calling something cliche generally does; the fact that everyone knows it’s coming is what gives it its value, to some extent. When applied to online communities it’s basically “meme” though.
The phrase he uses here is actually used to refer to someone who is dependable and decisive when it counts, so given what he’s saying he’s willing to do here, it’s understandable Megumin’s reaction is “I don’t think you’re really using that phrase right…”
The normal version of the phrase for “I’m back” is “tadaima,” but Aqua is saying “tadama” instead, which is a silly-sounding way of saying it you don’t generally see outside the internet.
The normal response to “tadaima” is some variant on “okaeri,” and in the second shot she’s saying “where’s my okaeri???” It’s supposed to be adorable in that Aqua sort of way, though I’m not sure it quite comes across the same in the translation.
The “Loli-maniac” here is actually “Lolima,” a (blunt) play on his name, Kazuma. Adding
“-ma” to the end of a word can also be a way of indicating “a criminal related to whatever the -ma is attached to.” One example is “toori-ma,” which is a word for someone who causes harm to random people on the street (basically like a serial killer). Toori is from the verb tooru, which means to pass by something (among other things; it’s a very versatile verb). Another is the word for pyromaniac/arsonist, houka-ma, where houka means to set something on fire (in an arson-y kind of way).
The word shes uses here is “bocchi,” which is a term that comes from “hitori-bocchi,” meaning “all alone.” Bocchi itself is slang that’s caught on a lot in recent years, especially in nerdy communities, and basically means “a person with no friends.” It’s a phrase you’ll see pop up a lot in manga and anime.
These resemble large konpeito, popular star-burst shaped candies. I can’t say for sure how intentional it is, but I know my reaction was “lol the first thing she reached for was candy.”
A more direct translation of this item’s name is “the crystal that improves your relationship.” The subs seem to imply Yunyun is talking about it like she could use it to make other friends, but in the Japanese she’s more saying “so this will make me and Megumin get closer?” Likewise, the subs line for Megumin implies she doesn’t care about making friends in general, while the Japanese is more “I see no reason to get along better with Yunyun.”
The opening line of the letter in the Japanese implies more “I haven’t been able to send reports lately/until now,” which I’m guessing is a reference to the gap between S1 and S2.
The phrase translated as “side jobs” here is “naishoku,” which is a type of job that you do from home. Typically it referred to jobs like mentioned here, folding fake flower or boxes: a company will deliver unfolded ones to your house, you fold them, then they pick them back up and pay you for however many were folded. The fake flowers one in particular is something that gets used in a lot of anime/manga as something super poor households do to earn money for food or whatever. In real life, it’s traditionally work that housewives would do if they had free time/needed to help supplement the family income.
Nowadays it can refer to various other types of work-from-home jobs, though with the nuance of it not being a “real”/full-time job, even if you can/could make enough money to live on with it (e.g. streaming/blogging).