omg you got spoiled about the second tattoo
but if you wanna know the signification for this tattoo let me quote the novel:
"« Socius.
– It means companion, member, or kin. The versatility of Latin!
“I know that much.”
I’d looked it up on a dictionary app on the way back.
The fact that the ‘membership’ wristband had burned up, leaving behind a word meaning ‘member’, seemed fairly connected, but what mattered more was this.
“But other people don’t seem to be able to see it. What do you think the reason is?”
– Oh dear, it seems they all have poor eyesight! I can see it quite well.
So creatures within ghost stories can see this?
“Glad you can see it.”
I rephrased my question.
“Then, what role do you think this mark serves?”
– It’s a mark granting you certain qualifications.
Without hesitation, Braun responded in a cheerful tone.
– You know how VIPs sometimes attend talk shows as special guests? They’re often given distinctive marks that set them apart from the other audience members, like a name tag or badge!
– Such a ‘distinguished mark’ grants privileges like special seating, rehearsal viewing, or backstage access!
I instinctively raised my arm to look at the mark.
“…So, this is like a ‘special qualification’?”
– Well, at least to the theme park mascots, yes. »
I think this convo between Braun and Soleum will get adapted in the next chapter btw

wait wat dat tattoo mean….