Generally, you owe income tax to the state where you physically live or perform the work on all your worldwide income, regardless of where the company is located. There are 6 states (I think is the correct current number) that will sometimes tax you if you work remotely for an employer based in that state even if you live out of state. But South Carolina is not one of them.
You seem to say you live in California. If you worked remotely for a South Carolina employer but did not physically live or work in South Carolina at the time, you do not owe a SC tax return. However, if you visited SC and performed work in that state, you owe SC a non-resident return for income earned in that state. That income is also added to your CA income, but CA would give you a credit for out of state taxes you pay.
