is it legal and safe to put a 4 point seat harness in my car without actual racing seats?

This is without buying actual racing seats and keeping my original toyota corolla seats and just replacing the existing seat belts.
what is required?
remember LEGAL AND SAFE!
thank you for your help:]
any videos wuld help alot.

Do i need racing harness with my racing seats or will the stock seat belts be fine?

Im looking at buying some racing seats for my lancer when i start to customize it later this summer. Im not sure if i should get the harness’ with the seats or not. I mean would it look stupid with out them? also anybody know of street legal harness?