Probably a lot longer than it should lol. Based on the first chapter which I think takes place in the future, they might not figure it out at all....
Little spoiler...
It will take a long time for the MC... Jigu will learn about Neuta's identity first and MC well, he got a long...loooonnggg way to go before he figure out who Ji9star is.
Jigtars founds out first bit for what I know even when they were gonna meet IRL, MC still didn't know
That's funny I figured it would be the other way around lol
Even tho Neuta figured it out too late, it became so funny when he learned about Ji9star identity
Now that they’ve heard each other’s voices, I wonder how long it will take for them to put two and two together that they have the same voices as each other’s neighbors