When she says “that” here, she refers to it as “その子 (sono ko),” basically referring to it as a child and showing how attached she is to it.
The way he says the part about the debt, (借金は減らない shakkin wa heranai) implies more that the debt isn’t going down, which sounded to me like they are paying it back, just in small enough amounts that it’s not actually shrinking it (either due to interest making it grow or it just being so big the amounts they’ve paid are insignificant).
I don’t actually know whether that’s true or not, but it’s the impression I got from how the line was worded.
The line here “心配させやがって shinpai sase yagatte” is basically “you had us worried” with the yagaru (conjugated as yagatte) excluded. Yagaru is a word you stick on the end of a verb that someone else has performed to indicate disdain/displeasure with the fact they did it. Usually it’s pretty rude and common to use when you’re angry at somebody, but in some cases between friends it basically serves as emphasis—pairing it with “causing worry” like seen here is common, in sort of a “you motherfucker, you worried the hell out of us!” kind of way (but not quite that vulgar).
These arranged marriage meeting (お見合い o-miai) things are still a thing in Japan nowadays, though less common. Basically the idea is that someone looking to get married will go through a third party (an agency that specializes in that sort of thing, or their parents’ network, etc.) who will find them someone that seems like would be a good match, and arrange a meeting between the two (usually showing a picture first, or rather several pictures and short profiles to choose from among). There’s no guarantee it will go anywhere and not too much commitment involved, but the explicit goal (in the modern context) is to start dating with the intent of getting married in the near future. It’s actually kind of like a marriage-focused precursor to online dating services.
The word for father she uses here (translated as “he”), is chichi (父). It’s a totally normal way to refer to your father when talking to non-family members…but it’s also a homophone for boobs (乳).
Kamiwaza (神業, “godly skills” here) originally refers to various rituals relating to kami, or feats of skill so impressive that they’re almost like something only a god could accomplish.
Probably it’s most common modern usage is in video games, to describe that sick 360 no-scope or something like this.
The original line just mentions her having to stop being an adventurer, it leaves any “with us” to be inferred by the listener.
In addition to laughing at “Lalatina,” part of the joke is that Darkness is speaking in very formal, “ladylike” language, which doesn’t exactly suit her character (at least as we/Kazuma/Aqua know it). Also the delivery of that wa at the end of the line sounds to me like it was supposed to sound forced, though maybe I’m just reading too much into it.
As an aside, wa as a sentence-ender can be used in gender-neutral ways, particularly when said with a descending tone, but when used with a rising tone is considered both feminine and sort of associated with fancy high-class language.
It’s trivial, but the phrase used for “pure” here is “kumori no nai 曇りのない,” a somewhat less poetic version of the same thing Aqua used in episode three. Basically the concept in both is that the eyes are unclouded [by greed/hate/other vices/etc.].
The fish here are, of course, koi, a popular and prestigious (and expensive) type of fish to have in gardens—not only in Japan, but abroad as well (where they are typically imported from Japan). I think these seem mostly to be of the Taisho Sanke variety, which have a white base with red and black patterning (Taisho comes from the fact they were first bred in the Taisho period, and Sanke means three colors).
There is a surprising level of depth to koi breeding, and breeders will go through several stages of selection, hand picking only the best, eventually narrowing down a starting pool of often over 200,000 at birth to just a few hundred at the end of the process. There some videos in English you can find here or here, or just through some googling.
If you’re ever near Niigata and have access to a car, a drive through the koi breeding areas in the mountains is a great way to spend a day.
Two (extremely) stereotypical elements of those marriage meetings are the parents sitting in at the beginning before bowing out, giving the two potential partners some privacy, and the question “Do you have any hobbies? (ご趣味は？Go-shumi wa?),” using that specific (and polite) phrasing.
You may have noticed he said “kawaii (可愛い)” here, which was translated as charming. You may also have thought, “but isn’t kawaii cute?” Well yes it is, but it’s also got a broader number of uses than just that. If you break down the kanji, it’s made of 可, which is used for things like acceptable/permissible/possible, etc., and 愛, the kanji for love (a more caring type of love, with passionate love being 恋 koi). Add the “adjectivizer” -i ending, and you’ve got a word that describes something that invokes feelings of love/affection, and so can range from cute to charming to lovable—though granted “cute” is the primary usage nowadays.
The word here is “hiku (引く),” a verb meaning “to pull.” It’s commonly used in contexts like this one to indicate something is creepy/gross/etc., as the speaker (or subject) is “pulling” back; you know, like leaning back/stepping back to create some distance because eww.
The names here are Kasuma and Kuzuma, both of which are in fact taking words for trash/garbage/etc. (kasu and kuzu) and portmanteau-ing them with his name. As you can see, they feel much less forced in the Japanese, but I guess there’s not much you can do about that unless you want to go with like Assuma or Scuzuma, which are their own brand of cringe-y.
The word here is dogeza (土下座), which is the word for getting on your knees and bowing such that your forehead touches the ground (though people don’t actually always touch head to ground). It’s the ultimate bow, used for the most sincere of apologizing or begging.
The word used here is shinsei (真性), meaning an inborn part of someone’s nature.
The word she uses for “already over” is jigo (事後), meaning “post- / after the [whatever]” but, especially when used by itself like here, is a common euphemism for “after sex.”
The laugh here (and all the other times she uses it in this episode) is fuhi, short for fuhihi, is a common laugh associated with having bad thoughts, kind of like “heh heh heh” or whatever in English. It’s also apparently associated with a meme created when Mika from Idolmaster Cinderella Girls used it when talking about how cute one of the other girls was, which itself was a joke on how Mika’s VA laughed like that out loud (in an embarrassing fashion) at a live event once. I don’t think this is particularly related to said meme though.
I learn the weirdest things doing these notes sometimes.
Maybe my ears are bad, but I’m fairly sure she just says Kazuma here, not one of the “trashy” nicknames.
“Tough love,” here and often in Japanese, is ai no muchi 愛の鞭, the “whip* of love,” which takes on a bit of extra meaning when said by Darkness.
*It can also be like, rod/stick, the kind from “spare the rod, spoil the child,” but generally muchi is the word for whip/lash so that’s typically the mental image.