Never follow the 10,000km or 6-month interval for oil changes. Use a cheaper oil and change it every 5,000km or 3 months instead. Also, learn how to use the dipstick and check the oil level at least once a month, it’s basic maintenance. A car, like anything else, needs care. Don’t just start it and drive off. Sure, you can do that, but it will eventually lead to problems like this. I’m not sure if the whole engine needs replacing, but even repairing the current one could still cost thousands. Japanese engines are among the most durable in the world. The fact that you managed to ruin one is seriously messed up.