They definitely would. The mage girl can easily calculate how much debt they would be in if they didn't do so. Unless, well, they don't have a functioning brain. And they are really that dumb, tbh. But the author probably realizes it is also weird to have a walking computer in the group but...
Do you really not understand, or do you know that you are wrong, so you try your best to pretend not to understand? The argument is about how MC hides how his debt works, not his friends. You will drop that conversation entirely once I show you that he actually hid it.
Also, what default? Don't...
You are sure quick to backtrack from "They already knew about the interest rate" to "Actually, it doesn't matter." No shit Sherlock, it matters. The mage girl is a literal calculator; if she know that his debt is compound, she would remind everyone to pay it off. They already did the math and...
Oh, right, I wonder what the next few pages are about...
Oh yeah, it is about how not a single person in the group has any idea what compound interest is, and the dude intentionally hid it the whole time. Can you actually read the manga before glazing it?
They know about 10% per day, but they...
Those people don't even know the existence of compound interest, let alone questioning it. And he intentionally hides the fact that his ability functions that way. Imagine borrowing money from the bank to buy a house and believing you can pay it off in 10 years until the bank goes, "Oopsie...
horrible premise ngl. "actually my loan is compound interest" is such a fucking douchebag move that I don't understand how the writer think it would make the dude the sympathetic victim here. Bro is a literal loan shark. The party also have zero reason to repay the debt, they can just yeet him...