There are a few recurring quirks about the writing of Princess Connect, and more generally about translating any Japanese writing to English. When translating scripts from the game, I try to handle these quirks in a consistent way. This page is my attempt at compiling things that often come up in translation, and the rules I try to follow to address them. The notes here are not specific to any episode in particular; episode-specific translation notes are shown on the same page as the translated episode itself.
Canonically, I consider the main character's name to be Yuuki, since this is the default name that comes pre-filled in the selection box when you start a new account. Voice acting lines never say the main character's name since it can be anything, but the script itself has places where the player's selected name gets substituted in.
With very few exceptions, I do not include untranslated honorifics (titles attached to names like -san or -chan) in translated text, and instead try to reflect their meanings using English titles or other choices of wording. The default choice is just to drop the honorific and write the character's name, so for example, ペコリーヌさん (Pecorine-san), ペコリーヌちゃん (Pecorine-chan), and ペコリーヌ様 (Pecorine-sama) would all just become "Pecorine." In most situations, this sounds natural enough.
Often times, though, one can add some more flavor to reflect the honorific. For instance, "-sama" can often be translated as "Lord" or "Lady," so Kokkoro's usual address of "Pecorine-sama" would become "Lady Pecorine," indicating the level of deference Kokkoro has. But it sounds unnatural for a shopkeeper to call their customers "my lord" (unless they actually are a noble of some kind) or, worse, "Lord Customer," even though the customary address in Japanese is お客様 (okyaku-sama); a simple "Sir" or "Ma'am" would probably make more sense. Basically, there aren't any hard and fast rules for honorifics, and how they should be translated depends on context. But these choices can have a big effect on how natural and readable a script feels.
The exceptions are basically cases like "Yunichan's," where the honorific has been absorbed into a name as part of a gag.
Japanese has many more commonly-used pronouns than English. The words 私 (watashi), 僕 (boku), あたし (atashi), 俺 (ore), うち (uchi), and 自分 (jibun) are all commonly-used equivalents of the first-person pronoun "I," and those are just the most common ones. The good news is, much like with honorifics, it's usually a decent choice to render them all of those "I," or to render all of あなた (anata), 君 (kimi), あんた (anta), お前 (omae) as "you," for instance. But, also like with honorifics, it's often possible to add some more color to the dialogue to reflect the tone of the pronoun. For instance, "omae" and especially "temee" and kisama" are used in hostile situations, so one could consider translating them as "you bastard," or something similarly confrontational, if said in a fight.
Of course, Japanese speakers also omit pronouns frequently when the subject is clear from context. It should go without saying, but determining the actual subject of the sentence is important when translating these phrases, as it's usually not acceptable to omit the subject in English.
People's names can also be used slightly differently in Japanese. In both English and Japanese, it would be natural for someone to say ペコリーヌはよく食べるんだね ("Pecorine wa yoku taberunda ne") or "Pecorine sure eats a lot" to a third person who isn't Pecorine. However, if one were to directly say "Pecorine sure eats a lot" in English to Pecorine (assuming both were native English speakers), it would sound strange -- we would just use the second-person ("You sure eat a lot") directly instead of the third-person. In contrast, in Japanese, directly saying ペコリーヌはよく食べるんだね to Pecorine is completely normal; in fact, in formal situations, using a person's name (plus a suitable honorific, usually -san) is usually preferred to using a pronoun like あなた. In these cases, adding an extra "you" is often all one needs to do to get a better translation, e.g. "Pecorine, you sure eat a lot."
Names can also be used to fill in for first-person pronouns -- Miyako does this, for instance. In Japanese, this is considered cute and somewhat childish. In English, however, referring to oneself in the third person usually sounds awkward, and may suggest some sort of psychological dissociation. As such, a line like "ミヤコ：ミヤコは幽霊だから、壁なんて関係ないの～♪" would be better translated as "Miyako: I'm a ghost, so walls don't matter!" instead of "Miyako: Miyako is a ghost, so walls don't matter!"
It's common for Japanese speakers (and especially video game characters) to refer to each other by nicknames, or other styles that don't include the subject's actual name. This is especially common for Yuuki, since his name isn't fixed, so many characters use these styles to avoid having to say his name, like Kokkoro's 主さま (aruji-sama) or Eriko's 貴方様 (anata-sama). I just handle these case-by-case, making sure to keep the translations consistent for each one. So Kokkoro's "aruji-sama" always becomes "Master," while Eriko's "anata-sama" becomes "Lord Yuuki" or "my lord."
I mention this separately because it can be particularly tricky. 兄 (nii) and 姉 (nee) mean "brother" and "sister" respectively, and can be paired with honorifics like -san and -chan. These can be used to address one's siblings. But they can also be used by young children to address slightly older boys and girls, and this is often used towards Yuuki, for instance by Rino, Kurumi, Mimi, and Misogi. My rule is to only translate these as "brother" (or "sister") when the speakers actually consider themselves to have (or specifically want to have) a sibling relationship towards the subject. So, Rino and Kurumi both qualify -- Rino because she grew up with him that way, and Kurumi because she considers him as "adopted" into the Sarendia family. But Mimi and Misogi don't, because (as far as I know) they never actually claim that they have, or specifically want to have, any actual family ties with Yuuki.
The game script often uses Unicode symbols like ☆ or ♪ to end sentences; this is pretty common in manga writing generally. The most memorable example in the game is Pecorine's やばいですね☆ (yabai desu ne), which often comes with the ☆ at the end. I choose not to include these symbols just because it's not standard in English, and inputting the characters is also sometimes a hassle.