Is there a way to rename the characters? Not the MC but the NPCs?
Yes there is.
In your Glassix folder, open up data\lang\[language abbrevation]\[character name].xml
As an example:
Glassix 0.33.0\data\lang\en\motherA.xml
Caveats:
1: Opening these xml files in Notepad++ throws a parsing error. Ignore these.
2: If a character's name is written in scene dialogue, then it won't change. Find & Replace All is your friend here.
As for your consternation, here's a rundown:
angelA: Anael
businessA: Shiho
classmateA -> classmateC: Rin, Ayumi, Hikari
copA: Shizuru
copB: Iyo
demonA: Lily
lifeguardA -> lifeguardC: Eimi, Yae, Wakana
maidA: Ryoko
maidB *
merchantA -> merchantE: Daisuki, Nabila, Kristina, Atsuko, Romita
motherA, motherB: Aiko, Naomi
nurseA, nurseB: Hanae, Miwa
principalA: Mitsuko
secretaryA -> secretaryD: Fujiko, Yatsumi, Utako, Marylin
sisterA, sisterC: Kana, Kumiko
stewardessA, stewardessB: Penny, Emika
teacherA -> teacherC: Saiko, Okimi, Sarah
tellerA -> tellerB: Kinu, Tokie
waitressA -> waitressC: Chan-Mei, Yurika, Emiri
* It's a blank file with no character data. You can safely skip this one.