Implication of "true name/真名" and its usage here

Question

真名にはこういう判断の仕方もあるのか

I met this sentence while reading a story containing a monologue of a character talking about "true name/真名" usage. I'm not a native Japanese and don't know much about this matter. I Hope someone can explain what this character means here about the usage of a person's true name.

My guess, but not sure about its implication : "So a person's true name also has this kind of usage, where it can be used to judge people's relationship, huh?" - Feel free to correct if you see my understanding is wrong somewhere.

Story: The main character saw 3 of his friends one night (they're 3 sisters 桃香/愛紗/鈴々) standing on top of the city's castle wall. He felt it had been like a long time since the last time time he saw the 3 of them stand together. (PS: the main character is working for a clan leader/ city governor 桃香, who is the eldest sister amongst the 3 sisters. They called him their master because in the past he saved the clan leader's life.)

桃香「あ……ご主人様」
その日の夜。城壁の上にいたのは、桃香たち三人だった。
Main character「なんだか、三人がそうやって揃ってるのを見るの……久しぶりだな」
愛紗「そうですね。鈴々も長い事、青州の賊討伐に出ていましたから」
鈴々「ずーっと星と一緒だったから、肩がこったのだ」
愛紗「あの口ぶりが移らんだけマシだろう」
桃香「あはは……。でも、趙雲さんと仲良くなったんだね」
そういえば、趙雲の真名を呼んでるもんな。なるほど、真名にはこういう判断の仕方もあるのか…

(* forgot to mention the character 趙雲 mentioned in this dialogue is a mercenary, who's also fighting alongside the main character's faction. This character likes to tease others and the character 愛紗 doesn't like her)

Answer 1

Based on the names mentioned in that quote, you're playing one of the games from this franchise?

恋姫†無双

『三国志』の世界を舞台としたアドベンチャーゲームだが、武将を初めとした登場人物が、本作ではほぼ全員女性として登場する（その理由は本編中で語られる）。

また、ゲーム独自の設定として女性武将は“真名”（まな）という姓・名・字以外の名を持つ。この“真名”は、本人が心を許した証として呼ぶことを許した名前であり、本人の許可無く“真名”で呼びかけることは、問答無用で斬られても文句は言えないほどの失礼に当たる。

From a meta perspective, I imagine they implemented this 真名 system because the original male names from 三国志, such as 趙雲, would sound too stern and distracting in a bishojo eroge. In any case, this is a setting unique to this franchise, and shouldn't be considered directly related to real Chinese or Japanese history.

Generally speaking, the concept of 真名 is not relevant in modern Japan, and it's basically something that sometimes appears in fantasy/isekai works. Those who aren't particularly familiar with such genres may not have heard the term itself. While definitions vary greatly from work to work, they tend to be based on this definition from the English Wikipedia — that is, secret names that are tightly tied to one's spirit, often possessed by mystical beings like gods or demons, and must not be known by others. So if anything, 真名 is a western concept!

In real historical Japan over 150 years ago, noble samurai used two or more different names, but none of them were particularly mystical or meant to be kept secret. Conceptually, 諱 might be loosely related to the 真名 system in your game, but they're not the same. You can read about the history of Japanese names in this article: A Long History of Japanese Names

Your understanding of the sentence "真名にはこういう判断の仕方もあるのか" seems just fine to me.

Answer 2

My guess, but not sure about its implication : "So a person's true name also has this kind of usage, where it can be used to judge people's relationship, huh?"

Your original translation seems close to the truth, but I'd probably say it like: "So a person's true name can also be used to judge, huh"

The message is the same but it's important to look from the right viewpoint.

As for 真名, it's already quite an ancient word and doesn't get used in daily conversation that much. It can have the meaning of both "Real name" & "Kanji", and can also be read as まんな.

It's used to emphasize the fact that something is written in kanji and there are words like 真名本(まなほん), which means "a book written entirely in kanji". This usage is probably more common than "Real name", despite it being marked archaic by most dictionaries.

Either way, you shouldn't get too hung on an archaic word.